For the cupcakes:
2 cups all-purpose flour
¾ cup unsweetened cocoa powder
1 tablespoon espresso powder
1 teaspoon baking soda
½ teaspoon salt
2 cups sugar
2 sticks (1 cup) unsalted butter, at room temperature
4 large eggs, at room temperature
2 teaspoons vanilla extract
1 cup brewed coffee
1 cup toffee bits
For the ganache and toffee layer:
8 ounces bittersweet chocolate, finely chopped
1 cup heavy cream
3 tablespoons unsalted butter, at room temperature
1½-2 cups toffee bits
For the frosting:
5 large egg whites
1½ cups sugar
4 sticks (2 cups) unsalted butter, at room temperature
½ teaspoon coarse salt
1 tablespoon vanilla extract
⅓ cup caramel sauce
To make the cupcakes, heat oven to 350º. Line cupcake pans with paper liners. Whisk together the flour, cocoa powder, espresso powder, baking soda and salt in a medium bowl and set aside.
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter and sugar together at medium-high speed for 2-3 minutes, or until light and fluffy. Add the eggs one at a time, beating well after each addition, and scrape the sides and bottom of the bowl as needed. Blend in the vanilla.
With the mixer on low speed, alternately add the flour mixture and the coffee, starting and ending with the flour. Mix until just incorporated. Fold in the toffee bits with a spatula.
Divide the batter evenly between the prepared liners. Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean. Allow to cool in the pans 5-10 minutes before transferring to a wire rack to cool completely. Once the cupcakes are cool, core them using your desired method (I promise the finger trick is really fast and easy!).
To make the ganache, place the chopped chocolate in a heatproof bowl. Bring the cream to a simmer in a small saucepan. Remove from heat and pour the hot cream over the chocolate; let stand 1-2 minutes, then whisk together until a smooth ganache forms. Whisk in the butter 1 tablespoon at a time until completely melted and incorporated. Chill the ganache in the refrigerator or freezer until it reaches a pipeable consistency, whisking every 5-10 minutes to ensure even cooling. Once the ganache has thickened slightly, transfer it to a pastry bag. Cut a small opening in the bag and fill each cupcake with ganache. Place the toffee bits in a bowl. Pipe a ring of ganache around the top of each cupcake, leaving a hole in the center. Dip the ganache portion of each cupcake into the toffee, pressing gently to adhere.
To make the frosting, combine the egg whites, sugar and salt in the bowl of a stand mixer set over a small saucepan of simmering water. Whisk constantly by hand until the sugar has dissolved. Test by rubbing the mixture between your fingers; you shouldn’t feel any grittiness.
Attach the bowl to the stand mixer fitted with the whisk attachment. Begin mixing on low speed and gradually increase to high and whip until stiff peaks form. Continue mixing until the mixture is completely cool (test by feeling the bottom of the bowl) and light, fluffy and glossy. This should take about 10 minutes but may take longer.
Replace the whisk attachment with the paddle attachment. Set the mixer to medium-low and add the butter, 2 tablespoons at a time, mixing well between each addition. Once all the butter has been incorporated, increase to medium speed and beat until fluffy. Blend in the vanilla and caramel until smooth and completely incorporated, scraping down the sides of the bowl as needed.
Place the frosting in a pastry bag with a decorative tip and top each cupcake with a swirl of frosting. Sprinkle with additional toffee pieces, if desired.