Let’s embark on creating this spectacular Turtle Chocolate Layer Cake! It’s best to start with the caramel sauce as it needs to cool completely.

Make the Salted Caramel Sauce: In a medium to large, heavy-bottomed saucepan, combine the 2 cups granulated sugar and 1 cup water. Stir gently over medium-low heat just until the sugar is completely dissolved (no more graininess). Stop stirring. Increase heat to medium or medium-high and bring the mixture to a boil. Do NOT stir from this point on, as stirring can cause crystallization. Let the mixture boil undisturbed, watching the color carefully. Occasionally, you can gently swirl the pan if needed for even coloring. Boil until the mixture turns a deep golden amber color (like copper or dark honey) – this can take 15-25 minutes depending on your stove. Have your butter and room temperature/warm cream measured and ready nearby.

As soon as the caramel reaches the desired deep amber color, immediately remove the pan from the heat. Carefully add the butter pieces – the mixture will bubble up intensely. Whisk quickly until the butter is melted and incorporated. Now, very slowly and carefully stream in the heavy whipping cream while whisking constantly. The mixture will bubble furiously; keep whisking until it subsides and the sauce is smooth. Stir in the 1 tbsp vanilla extract and 1 tsp salt. Taste carefully (it’s hot!) and add more salt if desired for a prominent salted caramel flavor. Pour the finished caramel into a heatproof jar or bowl and let it cool completely at room temperature, then chill in the fridge until needed (it will thicken significantly as it cools). Can be made up to a week ahead.

Make the Chocolate Cake Layers: Preheat oven to 300°F (148°C) (note the lower temperature). Prepare three 8-inch round cake pans with grease and parchment paper bottoms. In a large bowl, whisk together the flour, granulated sugar, sifted cocoa powder, baking soda, and salt. In a separate medium bowl, whisk together the room temperature eggs, room temperature milk, vegetable oil, and vanilla extract. Pour the wet ingredients into the dry ingredients and mix (by hand or low speed mixer) until just combined. Carefully stir in the hot water (or coffee) until the batter is smooth and thin.

Divide the thin batter evenly among the three prepared pans. Bake for 30-33 minutes, or until a wooden toothpick inserted into the center comes out clean or with a few moist crumbs. Let cool in pans on wire racks for 10 minutes, then invert onto racks, remove parchment, and cool completely.

Make the Caramel Buttercream: Ensure your butter is at room temperature and your prepared caramel sauce is also at room temperature (or slightly cool, but spreadable). In a large mixer bowl (stand mixer with paddle recommended due to volume), beat the butter on medium-high speed for 3-5 minutes until very pale and fluffy. Reduce speed to low and gradually add the 10 cups of sifted powdered sugar, about 2 cups at a time, mixing until just incorporated after each addition. It will be very thick. Add about 1/2 cup of the room temperature caramel sauce and the salt (start with 1/4 tsp). Beat on medium speed until combined and smooth. Gradually add more caramel sauce (up to 3/4 cup total) until the desired flavor and a smooth, spreadable consistency is reached. Be careful not to add too much liquid and make the frosting too soft. Beat on medium-high for another minute or two until fluffy. Taste and adjust salt if needed.

Toast the Pecans: Spread chopped pecans on a baking sheet and toast at 350°F (175°C) for 5-8 minutes until fragrant. Let cool completely.

Assemble the Cake: Level the tops of the completely cooled cake layers if necessary. Place the first layer on your serving plate/stand. Transfer about 1.5-2 cups of buttercream to a piping bag fitted with a large round tip (or snip corner). Pipe a thick dam (ring) of buttercream around the top outer edge of the cake layer. Spread about 2/3 cup of buttercream evenly inside the dam. Pour about 1/2 cup of the cooled caramel sauce over the buttercream inside the dam and spread gently. Sprinkle about 1/4 cup (or more) of the toasted chopped pecans over the caramel.

Carefully place the second cake layer on top. Repeat the process: pipe dam, spread buttercream inside, pour caramel sauce, sprinkle pecans. Place the third and final cake layer on top (upside down for flat top). Apply a thin crumb coat of the caramel buttercream all over the cake. Chill for 30-60 minutes until the crumb coat is firm.

Frost the top and sides of the cake smoothly with the remaining caramel buttercream using an offset spatula. Chill again briefly if desired before adding ganache.

Make the Chocolate Ganache: Place chopped semi-sweet chocolate chips in a heatproof bowl. Heat 1/2 cup heavy cream until just simmering. Pour hot cream over chips, let sit 2-3 minutes, then whisk until smooth. Let cool slightly until it reaches drip consistency (cool but fluid).

Drizzle the ganache around the top edge of the chilled cake, letting it drip down the sides. Pour remaining ganache on top center and spread gently. Let the ganache set slightly (10-15 mins, chilling helps). Pipe decorative swirls or rosettes with any reserved buttercream around the top edge. Garnish generously with more toasted chopped pecans and an optional drizzle of leftover caramel sauce over the piped swirls/pecans. Refrigerate until serving, but let sit out before slicing.