Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.

In a mixing bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Add softened butter, eggs, buttermilk, bourbon, and vanilla extract. Mix until smooth and well combined.

Divide the batter evenly between the prepared cake pans.

Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.

Let the cakes cool in the pans for 10 minutes, then transfer to wire racks to cool completely.

In a mixing bowl, beat the softened butter until creamy.

Gradually add cocoa powder and powdered sugar, mixing until combined.

Add bourbon, vanilla extract, and milk as needed to achieve desired consistency.

Place one cake layer on a serving plate. Spread a layer of frosting on top.

Place the second cake layer on top and frost the top and sides of the cake.

Decorate as desired and serve.