For the cupcakes:
2 2/3 cups all-purpose flour
2/3 cup unsweetened cocoa powder
2-3 tsp. espresso powder
2 tsp. baking powder
1 tsp. baking soda
½ tsp. salt
1 cup whole milk
1 cup strong brewed coffee
1 tsp. peppermint extract
1 cup (2 sticks) unsalted butter, at room temperature
1 cup granulated sugar
1 cup light brown sugar
2 large eggs

For the frosting:
6 large egg whites
1¾ plus 2 tbsp. granulated sugar
1½ cups (3 sticks) unsalted butter, at room temperature
4 tsp. peppermint extract
1-2 tsp. vanilla extract