Makes 12-16 (I got 15)
1 1/3 cups all-purpose flour
1/3 cup unsweetened cocoa powder
1 tsp baking powder
1/2 tsp baking soda
1/4 tsp salt
2 teaspoons ground coffee
1/2 cup whole milk
1/2 cup strong brewed coffee, at room temperature
1/2 cup (1 stick) unsalted butter, at room temperature
1/2 cup granulated sugar
1/2 cup firmly packed light brown sugar
1 large egg, at room temperature
Position a rack in the middle of the oven and preheat to 350°F. Line a standard 12-cup muffin pan with paper or foil liners.
Sift together the flour, cocoa powder, baking powder, baking soda, and salt into a bowl. In a measuring cup, combine the milk and brewed coffee. In a medium bowl, using an electric mixer on medium-high speed, beat the butter and sugars together until light and fluffy, 2-3 minutes. Add the egg and beat until combined. Add the flour mixture in 3 additions, alternating with the milk mixture in 2 additions, beating on low speed until just combined; scrape down the sides of the bowl as needed.
Divide the batter evenly among the prepared muffin cups, filling each about ½ to ¾ full. Bake until a toothpick inserted in the center of a cupcake comes out clean, 16-20 minutes (book says 22-24 minutes, mine were done at 16). Let the cupcakes cool in the pan on a wire rack for 5 minutes. Transfer the cupcakes to the wire rack and let cool completely, about 1 hour.
Coffee Swiss Meringue Buttercream
3/4 cup granulated sugar
3 egg whites
1/8 tsp salt
3/4 cup (1 1/2 sticks) unsalted butter, at room temp
1 tbsp hot water
1 1/2 tsp instant coffee
Put sugar, egg whites and salt into the top of a double boiler over a pan of simmering water. Whisking constantly, cook until sugar has dissolved and mixture is warm (about 160 degrees). Pour heated egg whites into the bowl of an electric mixer fitted with the whisk attachment. Beat egg white mixture on high speed until it forms stiff (but not dry) peaks. Continue beating until fluffy and cooled, about 7 minutes total. Switch to the paddle attachment. With mixer on medium-low, add butter two tablespoons at a time, beating well after each addition. Increase speed to medium-high; continue beating until frosting appears thick, about 3 minutes. Meanwhile, stir 1 1/2 tsp instant coffee into 1 tbsp hot water until dissolved, then put it in the refrigerator or freezer until it comes down to room temperature. Reduce mixer speed to low and add coffee mixture. Continue beating 1 minute to reduce air bubbles.