Step 1

Preheat oven to 350°F. Coat 3 (8-inch) round cake pans with baking spray. Line bottoms of pans with parchment paper; coat paper with baking spray. Whisk together granulated sugar, flour, cocoa, baking powder, baking soda, and salt in a large bowl. Whisk together eggs, milk, oil, bourbon, and vanilla in a small bowl; add to flour mixture, and whisk until just combined. Add hot water to batter; whisk until combined.

Step 2

Divide batter evenly among prepared pans (about 1 ½ cups each). Bake in preheated oven until a wooden pick inserted into centers of cakes comes out clean, 22 to 25 minutes. Cool in pans 10 minutes. Transfer to a wire rack; cool completely, about 45 minutes.

Step 3

Measure ⅓ cup Browned Buttercream Frosting into a piping bag fitted with a star tip; set aside.

Step 4

Spread remaining Browned Buttercream Frosting between cake layers and on top and sides of cake. Pipe reserved frosting in piping bag around top edges of cake.