Raspberry-Rhubarb Slab Pie

Introduction

Craving a vibrant, tangy dessert that’s perfect for feeding a crowd? What if you could combine the tartness of rhubarb with the sweet juiciness of raspberries in a shareable, golden-crusted pie? Say hello to Raspberry-Rhubarb Slab Pie! This delightful treat features a buttery, flaky crust encasing a bright, fruity filling, baked in a sheet pan for easy slicing. Ideal for potlucks, picnics, or family gatherings, it’s a show-stopping dessert that balances ease and elegance. Ready to create some tart-sweet magic? Let’s grab a rolling pin and get baking!

Overview

Raspberry-Rhubarb Slab Pie is a large-format pie with a homemade double crust and a filling of rhubarb, raspberries, and a sweetened cornstarch base, baked in a 9×13-inch pan. What makes it special? The combination of tart rhubarb and sweet raspberries creates a vibrant filling, while the slab format ensures generous servings with a perfect crust-to-filling ratio. This moderately easy recipe takes about 1 hour 15 minutes (25 minutes prep, 50 minutes baking, plus chilling and cooling) and serves 12, making it ideal for group gatherings.

• Time Requirement: 1 hour 15 minutes (25 minutes prep, 50 minutes baking, plus 1 hour chilling and cooling)
• Difficulty Level: Moderate (requires dough-making and rolling skills)
• Servings: 12 slices

Essential Ingredients

The magic of Raspberry-Rhubarb Slab Pie lies in its fresh, balanced ingredients. Here’s what you’ll need and why each one matters:

For the Crust

• All-Purpose Flour (2½ cups): Forms the base of the flaky, buttery crust.
• Salt (1 tsp): Enhances the crust’s flavor and balances sweetness.
• Granulated Sugar (1 tsp): Adds a subtle sweetness to the crust.
• Unsalted Butter (1 cup, 2 sticks, cold and cubed): Creates a flaky, tender crust through cold fat pockets.
• Ice Water (6–8 tbsp): Binds the dough without warming the butter, keeping the crust flaky.

For the Filling

• Rhubarb (3 cups, chopped): Provides a tart, tangy backbone to the filling.
• Fresh Raspberries (2 cups): Add sweet, juicy flavor and vibrant color.
• Granulated Sugar (1 cup): Sweetens the filling, balancing the tartness of rhubarb and raspberries.
• Cornstarch (¼ cup): Thickens the filling to prevent a runny pie.
• Lemon Juice (1 tbsp): Brightens the flavors and enhances tartness.
• Vanilla Extract (1 tsp): Rounds out the filling with a warm, aromatic note.

For the Topping

• Egg (1, beaten): Creates a glossy, golden crust when brushed on as an egg wash.
• Coarse Sugar (1 tbsp, optional): Adds a sparkly, crunchy finish to the crust.

Substitutions and Variations

• Flour: Use a 1:1 gluten-free flour blend for a gluten-free crust, adding 1 tsp xanthan gum if not included.
• Butter: Swap with vegan butter for a dairy-free crust, ensuring it’s cold.
• Sugar: Use brown sugar or coconut sugar in the filling for a deeper flavor; reduce to ¾ cup for a tarter pie.
• Rhubarb: Substitute with chopped strawberries or additional raspberries, maintaining 5 cups total fruit.
• Raspberries: Use frozen raspberries (no need to thaw) or blackberries for a different berry flavor.
• Cornstarch: Replace with arrowroot powder or tapioca starch (¼ cup) for similar thickening.
• Lemon Juice: Swap with lime juice or omit for a milder filling.
• Egg Wash: Use milk or cream (dairy or plant-based) for a less glossy finish, or omit for a matte crust.
• Vegan Option: Use vegan butter, plant-based milk for the wash, and a flax egg (1 tbsp flaxseed + 3 tbsp water) or omit the egg wash.
• Gluten-Free: Use a gluten-free flour blend for the crust and ensure cornstarch is gluten-free.

Step-by-Step Instructions

Making Raspberry-Rhubarb Slab Pie involves crafting a flaky crust and a vibrant filling, with straightforward assembly. Follow these instructions for a perfect pie every time:

1. Make the Dough:
   • In a large mixing bowl, whisk together 2½ cups all-purpose flour, 1 tsp salt, and 1 tsp granulated sugar.
   • Add 1 cup cold, cubed unsalted butter and cut in using a pastry cutter, two forks, or your fingers until the mixture resembles coarse crumbs with pea-sized butter pieces, about 2–3 minutes.
   • Add 6–8 tbsp ice water, one tablespoon at a time, mixing with a fork until the dough begins to hold together when pinched (avoid overmixing).
   • Divide the dough into two equal portions, shape into flat disks, wrap in plastic wrap, and refrigerate for at least 1 hour (or up to 2 days).
   • Tip: Keep the butter cold to ensure a flaky crust, and add water sparingly to avoid a tough dough.
2. Preheat and Prepare:
   • Preheat the oven to 375°F (190°C).
   • Lightly grease a 9×13-inch baking pan (or quarter sheet pan) with butter or cooking spray to prevent sticking.
   • Tip: Use a metal or glass pan for even baking, and ensure it has at least 1-inch sides to contain the filling.
3. Prepare the Filling:
   • In a large mixing bowl, gently combine 3 cups chopped rhubarb, 2 cups fresh raspberries, 1 cup granulated sugar, ¼ cup cornstarch, 1 tbsp lemon juice, and 1 tsp vanilla extract.
   • Stir carefully with a spatula to coat the fruit without breaking the raspberries, about 1 minute. Set aside.
   • Tip: Chop rhubarb into ½-inch pieces for even cooking, and mix gently to keep raspberries intact.
4. Roll Out the Bottom Crust:
   • On a lightly floured surface, roll out one dough disk into a rectangle about 11×15 inches, large enough to fit the 9×13-inch pan with some overhang.
   • Transfer the dough to the prepared pan by rolling it loosely around the rolling pin, then unrolling it into the pan.
   • Press the dough into the corners and up the sides, letting excess hang over the edges.
   • Tip: Work quickly to keep the dough cold, and patch any tears with extra dough, pressing to seal.
5. Add the Filling:
   • Pour the rhubarb-raspberry filling into the crust, spreading evenly to ensure consistent thickness.
   • Include any sugary juices from the bowl for flavor.
   • Tip: Distribute the filling evenly to avoid thin spots, and gently shake the pan to settle the fruit.
6. Roll Out the Top Crust:
   • Roll out the second dough disk into a 10×14-inch rectangle for a full top crust, or slightly larger if making a lattice.
   • For a full crust: Lay the dough over the filling, trim excess to match the bottom crust, and crimp the edges by pressing with a fork or pinching to seal.
   • For a lattice: Cut the dough into ¾-inch-wide strips (about 10–12 strips). Lay half the strips vertically across the pie, spacing evenly, then weave the remaining strips horizontally to create a lattice pattern. Trim excess and crimp edges.
   • Tip: Chill the top dough briefly if it softens, and use a ruler for even lattice strips.
7. Apply Egg Wash:
   • In a small bowl, beat 1 egg and brush it lightly over the top crust (full or lattice) using a pastry brush for a golden, glossy finish.
   • Sprinkle 1 tbsp coarse sugar (if using) evenly over the crust for a sparkly, crunchy topping.
   • Tip: Apply a thin layer of egg wash to avoid pooling, and use coarse sugar for texture without overpowering sweetness.
8. Bake:
   • Place the pan in the preheated oven and bake for 45–50 minutes, or until the crust is golden brown and the filling is bubbling through the lattice or edges.
   • Check for doneness: the filling should be thickened and visibly bubbling to ensure the cornstarch has activated.
   • Tip: Place a baking sheet under the pan to catch drips, and cover edges with foil if browning too quickly after 30 minutes.
9. Cool and Serve:
   • Remove the pie from the oven and let it cool completely in the pan, about 2–3 hours, to set the filling for clean slicing.
   • Slice into 12 rectangles (3×4 grid) using a sharp knife, wiping clean between cuts.
   • Serve at room temperature or slightly warmed, optionally with vanilla ice cream, whipped cream, or a dusting of powdered sugar.
   • Tip: Cool fully to avoid a runny filling, and reheat slices briefly (350°F for 5–7 minutes) if serving warm.

Assembly

Assembling Raspberry-Rhubarb Slab Pie is all about creating a flaky, buttery crust with a vibrant, juicy filling that’s easy to slice and share. Here’s how to make it look and taste incredible:

• Assemble Thoughtfully: Roll the dough evenly, spread the filling uniformly, and crimp or lattice the top for a professional, rustic look.
• Preparation Tips:
  • Keep the dough cold during rolling to maintain flakiness, chilling briefly if it softens.
  • Chop rhubarb consistently and handle raspberries gently to preserve their shape in the filling.
  • Crimp edges securely to seal the filling, preventing leaks during baking.
• Presentation Tips:
  • Serve on a large platter or directly from the pan to highlight the golden crust and bubbly filling.
  • Garnish with a scoop of vanilla ice cream, a dollop of whipped cream, or fresh raspberries for a vibrant, inviting look.
  • Pair with lemonade, iced tea, or a sparkling wine for a complete dessert experience, perfect for picnics, potlucks, or holiday gatherings.
  • Use a sharp knife or pizza cutter to slice cleanly, showcasing the layered crust and colorful filling.

Storage and Make-Ahead Tips

Raspberry-Rhubarb Slab Pie is best fresh but can be prepped or stored with these tips to maintain its quality:

• Make-Ahead:
  • Prepare the dough up to 2 days in advance, wrap tightly, and refrigerate; let soften slightly before rolling.
  • Make the filling up to 1 day ahead, refrigerate in an airtight container, and stir before using.
  • Assemble the pie (without baking) up to 4 hours ahead, cover, and refrigerate; apply egg wash and sugar just before baking.
  • Tip: Don’t assemble too early, as the filling’s moisture may soften the crust; bake within a few hours for the best texture.
• Storage:
  • Store leftovers in the pan, covered with plastic wrap or foil, or transfer slices to an airtight container in the refrigerator for up to 3 days. The crust may soften slightly.
  • Reheat slices in a 350°F (175°C) oven for 5–10 minutes to restore warmth and crispness; avoid microwaving, as it softens the crust.
  • Tip: Store with parchment between slices to prevent sticking, and refrigerate promptly to preserve the filling.
• Freezing:
  • Freeze the baked pie (whole or sliced) for up to 2 months, wrapped tightly in plastic wrap and foil. Thaw in the fridge overnight and reheat at 350°F (175°C) for 10–15 minutes.
  • Freeze unbaked pie (assembled in a freezer-safe pan) for up to 1 month; bake from frozen, adding 10–15 minutes to the baking time and covering edges if browning too fast.
  • Tip: Label with the date to track freshness, and freeze in portions for easy reheating.

Recipe Variations

Raspberry-Rhubarb Slab Pie is versatile and fun to customize. Here are some creative twists to try:

• Strawberry-Rhubarb Slab Pie: Replace raspberries with 2 cups chopped strawberries for a classic pairing.
• Mixed Berry Slab Pie: Use 2 cups mixed berries (raspberries, blueberries, blackberries) with 3 cups rhubarb for a colorful filling.
• Spiced Rhubarb Slab Pie: Add ½ tsp cinnamon and ¼ tsp ginger to the filling for a warm, spiced flavor.
• Citrus Raspberry-Rhubarb Pie: Mix 1 tsp orange zest into the filling and use orange juice instead of lemon for a citrusy twist.
• Gluten-Free Slab Pie: Use a gluten-free flour blend for the crust and ensure cornstarch is gluten-free.
• Vegan Slab Pie: Use vegan butter and a flax egg or plant-based milk for the wash.

Conclusion

You’re now ready to create a Raspberry-Rhubarb Slab Pie that’s as vibrant as it is delicious! This 1-hour-15-minute recipe is perfect for picnics, potlucks, or any gathering where you want to impress with minimal fuss. With its flaky crust, tart-sweet filling, and shareable format, this pie is a guaranteed crowd-pleaser. Feel free to tweak the fruits, spices, or crust design to make it your own. Grab your rolling pin, layer that filling, and enjoy every juicy, golden bite. Happy baking, and savor the raspberry-rhubarb bliss!

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FAQs

1. Can I use frozen rhubarb or raspberries?
Yes! Use 3 cups frozen rhubarb and 2 cups frozen raspberries without thawing to prevent excess liquid. Toss with sugar and cornstarch as directed; baking time may increase by 5–10 minutes.

2. Is this pie healthy?
It’s a dessert with butter and sugar. For a lighter version, reduce sugar to ¾ cup, use a whole-grain crust, or serve smaller slices with fresh fruit. Enjoy in moderation.

3. Can I make this vegan?
Yes! Use vegan butter, a flax egg (1 tbsp flaxseed + 3 tbsp water) or plant-based milk for the wash, and ensure sugar is vegan-friendly (some brands use bone char).

4. Why is my filling runny?
Insufficient cornstarch or underbaking can cause a runny filling. Ensure ¼ cup cornstarch is used, and bake until the filling bubbles vigorously to activate the thickener.

5. Can I use a different pan size?
Yes! An 8×12-inch pan works (same baking time); a 10×15-inch pan makes a thinner pie (bake 40–45 minutes). Adjust dough size slightly to fit, maintaining thickness.

6. How do I prevent a soggy crust?
Ensure the bottom crust is pressed firmly into the pan, bake until the filling bubbles, and cool completely to set the filling. Avoid overmixing the dough to keep it flaky.

7. Can I prep this for a party?
Yes! Assemble up to 4 hours ahead, refrigerate, and bake just before serving. Or bake up to 1 day ahead, store covered at room temperature, and reheat briefly at 350°F (175°C) for 5–10 minutes.

8. What’s the best way to store leftovers?
Store covered in the fridge for up to 3 days. Reheat in the oven to restore texture, and use an airtight container to prevent absorbing fridge odors.