Preheat oven to 350°F (175°C) and line four 8-inch cake pans with parchment paper, spraying the sides with cooking spray.
Sift 2 1/2 cups flour, 2 1/2 cups sugar, 1 cup cocoa powder, 2 1/2 tsp baking powder, 2 tsp baking soda, and 1 tsp salt.
Mix 1 1/4 cups warm water, 1 1/4 cups buttermilk, 2/3 cup oil, 3 eggs, and 2 tsp vanilla.
Combine the wet and dry ingredients until smooth.
Divide the batter into pans and bake for 22-25 minutes or until a toothpick comes out clean.
Let the cakes cool for 10 minutes, then freeze for 30 minutes.
Once cooled, flip the cakes out and level the tops if desired.
For caramel, heat 2 cups sugar until it turns amber, then stir in 3/4 cup butter, 1/2 cup heavy cream, and 1/2 tsp salt.
Let the caramel cool, then whip until it thickens. Set aside 1/3 cup for piping and mix 3/4 cup chopped peanuts into the rest.
Beat 1 1/2 cups butter and 1 cup peanut butter until fluffy.
Add vanilla, salt, 7 cups powdered sugar, and 2/3 cup heavy cream, mixing until smooth.
Place a third of the frosting in a piping bag and set aside the rest.
Stack and frost the cake, piping a buttercream ring and filling with peanut caramel between layers.
Chill the cake in the fridge or freezer to firm the frosting.
Drizzle caramel and chocolate ganache over the cake and top with Snickers pieces and sea salt. Enjoy!