Preheat the oven to 350ºF and prepare three 6-inch or two 8-inch cake pans by spraying the sides with cooking spray and fitting the bottoms with a wax paper or parchment cake circle.

Place all of the dry ingredients into the bowl of a stand mixer and stir on low for 30 seconds to fully combine them.

Add the vegetable oil, eggs, vanilla, and buttermilk and mix on low until just combined.

With the mixer still on low, add the hot water in a slow stream, then turn the mixer to medium and beat until smooth, about 2 minutes. The batter will be very thin.

Pour into prepared cake pans no more than ⅔ full and bake for 32-36 minutes, until a toothpick inserted comes out clean. Cool completely before filling and frosting.

In a large saucepan over medium heat, add the sweetened condensed milk, butter, brown sugar, corn syrup, heavy whipping cream, and salt. Stir with a rubber spatula constantly until the mixture is fully combined and begins to bubble, about 5 minutes.

Turn the heat to low and continue stirring until the caramel begins to thicken, 5-7 minutes. If you have a candy thermometer, you’ll want to cook this until it reaches 225F/107C.

Remove the caramel from the heat and mix in the vanilla extract, then fold in the chopped peanuts. Pour into a separate container and let the peanut caramel cool completely to room temperature before using it to fill the cake.

In the bowl of a stand mixer with the paddle attachment or using a hand mixer, whip the butter on high speed until smooth and creamy, about 3 minutes.

Add the powdered sugar, cocoa powder, marshmallow creme, peanut butter, and vanilla. Mix on low speed until fully combined, about 2-3 minutes, scraping down the bowl and paddle as needed.

In a stand mixer fitted with a paddle attachment, whip the butter on medium-high speed until creamy and light in color, 4-5 minutes.

Scrape down the bowl and paddle, then add powdered sugar, cocoa powder, milk, salt, and vanilla extract. Cover the mixer with a clean kitchen towel, then turn the mixer to low and mix until all ingredients start to come together.

Remove the kitchen towel, scrape down the bowl and paddle, then continue mixing on low speed until uniform and smooth, 2-3 minutes.

Once the chocolate cake layers have cooled completely, level and torte each layer to your desired height.

Add about 1.5 Cups of chocolate buttercream into a piping bag and snip off about ½ inch opening.

Place the first layer on a turntable and pipe a circle of chocolate buttercream around the edge of the cake layer, then pipe another circle of buttercream on top of the first to make it slightly taller.

Fill in the center halfway with the nougat filling and smooth it down. Then, fill nearly to the top of the chocolate buttercream circle dam with the peanut caramel filling.

Place the next cake layer on top and repeat the process of piping the chocolate buttercream circle and filling in the center with the nougat and peanut caramel fillings.

Place the final layer on top, upside down so that the bottom of the cake layer is the top of the cake.

For extra stability, wrap the sides of the cake in plastic wrap and place it in the refrigerator for about 20 minutes to let the fillings and the buttercream dam firm up.

To create the look pictured, crumb coat the cake with a thin layer of chocolate buttercream and refrigerate for another 10-15 minutes to let the frosting firm up.

Then, use the chocolate buttercream to frost a rustic textured finish with a small icing spatula.

Add chopped peanuts around the base of the cake, then add the rest of the chocolate buttercream into a piping bag fitted with Wilton Tip 1M and pipe swirls around the top of the cake.

Place a halved Fun-Size Snickers Bar between each swirl.