Preheat the oven to 350F. Line a small 9x13 baking sheet {not pan} with foil or parchment, spray with nonstick spray, and set aside.

In a small nonstick pot, melt the butter. Whisk in the cocoa, then the boiling water. Let the mixture boil for about 30 seconds, then set aside to cool.

In a medium bowl, combine the flour, sugar, baking soda, and salt. Pour the chocolate-butter mixture on top of the flour mixture, and whisk until well-combined and lump-free.

Quickly mix in the egg, followed by the vanilla, then the bourbon. Whisk until well-incorporated.

Pour batter into your prepared pan, and bake in preheated oven for 10-12 minutes. A toothpick inserted should come out clean, but the cake should not be dry! Set aside to cool as you prepare the frosting.

In a small bowl, beat the butter and sugar together with a hand mixer. Add in the vanilla and bourbon, and beat until smooth and fluffy. If frosting is too dry, add in a little milk as needed. Make sure frosting is not runny! Set in the fridge to chill until ready to assemble.

When you are ready to make the cake shots, use a shot glass to cut circles out of the sheet cake. For 12 cake shots, you should be able to get 24 circles.

Place a piece of cake at the bottom of each shot glass, top with some chilled frosting, top with another piece of cake, and more frosting.

Sprinkle cocoa powder on top for garnish, and either serve immediately or store in refrigerator until ready to serve. Enjoy!