Preheat your oven to 350°F (175°C). Line four 8-inch cake pans with parchment paper and lightly grease them. In a large bowl, whisk together the dry ingredients: flour, sugar, cocoa powder, baking powder, baking soda, and salt. In another bowl, mix the wet ingredients: warm water, buttermilk, oil, eggs, and vanilla until smooth. Gradually combine both mixtures, stirring gently until just combined.

Divide the cake batter evenly among the prepared pans. Bake for 22-25 minutes, or until a toothpick inserted into the centers comes out with a few moist crumbs. Let them cool in the pans for 10 minutes, then transfer to a wire rack and freeze for 30 minutes.

Prepare the peanut caramel while the cake layers cool. In a saucepan over medium heat, melt sugar, stirring until amber. Add butter and heavy cream, stirring until smooth. Set aside to cool slightly.

In a mixing bowl, beat unsalted butter and peanut butter until light and fluffy. Add vanilla, salt, and powdered sugar, mix until combined. Gradually add heavy whipping cream and beat until smooth and spreadable.

Layer the cake by placing one chilled layer on a serving plate. Spread peanut butter frosting, drizzle peanut caramel. Repeat with remaining layers. Chill the assembled cake briefly.

For ganache, heat heavy cream until simmering. Remove from heat, add chocolate chips, let sit, then stir until smooth. Cool until pourable.

Pour ganache over the cake, allowing it to drip down the sides. Drizzle additional peanut caramel, and decorate with chopped peanuts and mini Snickers bars.