Part 1: Baking the Moist Chocolate Cake Layers

1. Preheat and Prepare: Preheat oven to 350°F (175°C). Grease and flour three 8-inch round cake pans. Line the bottoms with parchment paper circles for easy release.
2. Combine Dry Ingredients: In a large bowl, sift together the all-purpose flour, granulated sugar, cocoa powder, baking soda, baking powder, and salt. Whisk to combine.
3. Combine Wet Ingredients: In a separate medium bowl, whisk together the eggs, buttermilk, vegetable oil, and vanilla extract.
4. Mix Batter: Add the wet ingredients to the dry ingredients and mix on low speed with an electric mixer (or by hand) until just combined. Do not overmix.
5. Add Hot Liquid: Carefully pour the hot water or hot coffee into the batter and mix on low speed until smooth. The batter will be thin – this is normal and what makes the cake moist.
6. Divide and Bake: Pour the batter evenly among the three prepared cake pans.
7. Bake: Bake for 25-30 minutes, or until a wooden skewer inserted into the center of the cakes comes out clean or with a few moist crumbs.
8. Cool: Let the cakes cool in the pans on a wire rack for 10-15 minutes before inverting them onto the rack to cool completely. Complete cooling is essential before frosting (at least 2-3 hours). Once cool, you can wrap them in plastic wrap and chill them; chilled cakes are easier to frost.

Part 2: Making the Peanut Butter Nougat Filling/Frosting

1. Beat Butter and Peanut Butter: In a large bowl using an electric mixer, beat the softened butter and creamy peanut butter together until light and fluffy, about 2-3 minutes.
2. Add Marshmallow Fluff (if using): Add the marshmallow fluff and beat until well combined.
3. Add Powdered Sugar: Gradually add the sifted powdered sugar, one cup at a time, beating on low speed until incorporated, then increasing speed to medium-high until smooth.
4. Add Vanilla and Salt: Beat in the vanilla extract and salt.
5. Adjust Consistency: Add heavy cream or milk, one tablespoon at a time, beating until the frosting reaches a spreadable consistency. You want it thick enough to hold its shape as a filling but still easy to spread. If it’s too thin, add more powdered sugar. If too thick, add a bit more cream/milk.
6. Chill (Optional): If the frosting seems too soft, you can chill it for 15-30 minutes to firm up slightly.

Part 3: Preparing the Salted Caramel Sauce (if homemade)

1. Dissolve Sugar: In a medium, heavy-bottomed saucepan, combine the granulated sugar and ¼ cup water. Stir gently over medium-low heat until the sugar is completely dissolved (no grainy texture). Avoid splashing sugar crystals on the sides of the pan.
2. Cook to Amber: Increase the heat to medium-high and bring the mixture to a boil. Cook, without stirring (swirl the pan occasionally if needed for even cooking), until the syrup turns a deep amber color, like honey. This can take 5-10 minutes. Watch it carefully as it can burn quickly.
3. Add Butter: Once amber, immediately remove the pan from the heat. Carefully whisk in the butter pieces one at a time until fully melted and incorporated. The mixture will bubble vigorously.
4. Add Cream: Slowly and carefully pour in the warmed heavy cream while whisking constantly. The mixture will bubble up again. Be cautious as the hot caramel can splatter.
5. Add Salt and Cool: Continue to whisk until the sauce is smooth. Stir in the sea salt. Let the caramel cool in the saucepan for at least 15-20 minutes (it will thicken as it cools). For cake filling, you want it to be thick but still pourable. If it gets too thick upon cooling, you can gently reheat it over low heat or in the microwave in short bursts.

Part 4: Assembling the Snickers Cake

1. Level Cakes (Optional): If your cake layers have domed tops, use a long serrated knife to level them for even stacking.
2. First Layer: Place one cake layer on your serving plate or cake stand. You can pipe a “dam” of peanut butter nougat frosting around the outer edge of the cake layer. This helps contain the caramel and peanuts.
3. Fill First Layer: Spread a layer of the peanut butter nougat frosting inside the dam (or over the whole layer if not using a dam). Drizzle generously with salted caramel sauce. Sprinkle with a third of the chopped roasted peanuts and a third of the chopped Snickers bars.
4. Second Layer: Top with the second cake layer. Repeat the dam, frosting, caramel, peanuts, and Snickers.
5. Third Layer: Add the final cake layer, top side down for a flat surface.
6. Crumb Coat: Apply a thin, even layer of the peanut butter nougat frosting all over the top and sides of the cake. This is the “crumb coat” which traps loose crumbs. Chill the cake in the refrigerator for at least 30 minutes to set the crumb coat.
7. Final Frosting: Frost the entire cake smoothly with the remaining peanut butter nougat frosting. You can reserve some for piping decorations later if desired. Chill the cake again while you prepare the ganache.

Part 5: Making and Applying the Chocolate Ganache Drip/Glaze

1. Heat Cream: Place the chocolate chips/chunks in a heatproof bowl. Heat the heavy cream in a small saucepan over medium heat until it just begins to simmer (don’t let it boil).
2. Make Ganache: Pour the hot cream over the chocolate. Let it sit for 5 minutes without stirring to allow the chocolate to melt.
3. Stir Until Smooth: Whisk the mixture gently from the center outwards until the ganache is completely smooth, glossy, and all the chocolate has melted.
4. Cool Slightly: Let the ganache cool for 10-15 minutes, stirring occasionally. It should be thick enough to create drips but still pourable. If it’s too hot/thin, it will run right off the cake. If it gets too thick, you can gently warm it in the microwave for 5-10 second intervals.
5. Apply Drip: Remove the chilled cake from the refrigerator. Using a spoon or a squeeze bottle, carefully drizzle the ganache around the top edge of the cake, allowing it to drip down the sides. Then, pour and spread the remaining ganache over the top of the cake, smoothing it out with an offset spatula.
6. Final Garnish: While the ganache is still wet, arrange the remaining chopped Snickers bars and roasted peanuts on top. You can also drizzle with extra caramel sauce.
7. Chill to Set: Refrigerate the cake for at least 1-2 hours (or preferably longer) to allow the ganache and frosting to set firmly before slicing and serving.