Preheat your oven to 350°F (175°C) and prepare three 6-inch cake pans by greasing them and lining the bottoms with parchment paper.

In a heat-safe bowl, combine 1 cup of unsalted butter and 8 ounces of semisweet baking chocolate. Microwave in 20-second intervals, stirring until melted and smooth.

In a separate mixing bowl, whisk together 1 cup of all-purpose flour, 1/2 cup of unsweetened cocoa powder, 1 teaspoon of baking powder, and 1/2 teaspoon of fine sea salt.

Once your chocolate mixture has cooled, whisk in 4 large eggs one at a time, followed by 1/2 cup of vegetable oil and 1 teaspoon of vanilla extract until fully combined.

Evenly divide the batter among the prepared pans and bake for 25 minutes. The edges should appear set and a toothpick inserted should come out with a few moist crumbs.

As the cake layers cool, prepare the frosting by beating together 1/2 cup of unsalted butter and 1 cup of creamy peanut butter until fluffy.

Place one cooled layer on a serving plate, spread about 1/2 cup of the frosting on top, then add the second layer, repeating the process.

Cover the cake lightly with plastic wrap and place it in the refrigerator for 15-20 minutes.

Carefully spread the remaining frosting over the entire cake, then prepare the ganache by heating 1/2 cup of heavy cream and pouring it over 4 ounces of chopped chocolate.

Pour ganache over the top of your cake, letting it drip down the sides.

Sprinkle chopped peanut butter cups on top for added texture and crunch before serving.

Store leftover cake covered at room temperature for 1 day, or refrigerate for up to 3 days.