Step 1: Prepare the Pickle-Brined Carrots and Walnuts (Optional, but Recommended). In a small bowl, combine 1/4 cup dill pickle brine and 1/4 cup water. Add 1 1/4 cups of the grated carrots. In another small bowl, combine another 1/4 cup of dill pickle brine and water. Add 1/2 cup of the chopped walnuts. Let both sit while you prepare the rest of the components.

Step 2: Preheat Oven and Prepare Baking Sheets. Preheat the oven to 350°F (175°C) with oven racks in the upper and lower thirds of the oven. Line 3 baking sheets with parchment paper; set aside.

Step 3: Cream Butter and Sugars. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, brown sugar, and granulated sugar on medium speed until pale and creamy, about 3 minutes.

Step 4: Add Eggs and Vanilla. Add the eggs and vanilla. Beat until well combined, stopping to scrape the sides of the bowl, as needed.

Step 5: Whisk Dry Ingredients. In a medium bowl, whisk together the flour, cinnamon, ground ginger, baking powder, baking soda, and salt.

Step 6: Combine Wet and Dry Ingredients. Gradually add the flour mixture to the butter mixture with the mixer on low. Beat until well combined, about 1 minute.

Step 7: Stir in Carrots and Walnuts. Drain the brined carrots very well, pressing out excess liquid. Drain the walnuts well. Stir in all the carrots (brined and regular) and all the walnuts (brined and regular) into the dough.

Step 8: Scoop Dough. Using a 1 ¾-inch cookie scoop, drop leveled spoonfuls (about 1 ½ tablespoons each) of the dough onto the prepared baking sheets, spacing at least 2 inches apart.

Step 9: Bake. Bake 2 pans at a time, rotating halfway through cooking, until the cookies are lightly browned around the edges, 14 to 16 minutes total.

Step 10: Cool. Cool the cookies on the pans for 3 minutes. Transfer to a wire rack to cool completely, about 30 minutes. Repeat with the remaining cookies.

Step 11: Make the Frosting. In the bowl of a stand mixer fitted with a paddle attachment, beat the cream cheese and butter on medium speed until smooth, about 3 minutes.

Step 12: Add Powdered Sugar, Vanilla, and Pickle Powder. With the mixer on low speed, add the powdered sugar, vanilla, and dill pickle powder, beating until combined.

Step 13: Beat Until Fluffy. Increase the speed to medium and beat until fluffy, about 2 minutes.

Step 14: Frost Cookies. Dollop a spoonful of frosting on the top of each cooled cookie and spread all over the top.

Step 15: Decorate (Optional). Sprinkle with orange jimmy sprinkles or chopped toasted (non-brined) walnuts, if you like. Garnish with fresh dill (optional).