For the cupcakes:
¾ cup unsweetened cocoa powder
1 tbsp. instant espresso powder
1½ cups all-purpose flour
1½ cups sugar
1½ tsp. baking soda
¾ tsp. baking powder
¾ tsp. salt
2 large eggs
¾ cup warm water
¾ cup buttermilk
3 tbsp. vegetable oil
1 tsp. vanilla extract

For brushing the cupcakes:
Kahlua liqueur

For the frosting:
12 tbsp. unsalted butter, at room temperature
4 cups confectioners’ sugar, sifted
7-8 tbsp. Kahlua liqueur
2 tbsp. heavy cream