Preheat the Oven
Arrange the oven racks in the upper and lower thirds. Preheat the oven to 350°F.
Line 22 muffin cups with paper liners.
Prepare the Batter
In a large mixing bowl, whisk together vodka, instant espresso, and 1/2 cup water until combined.
Add the cake mix, egg whites, and vegetable oil. Whisk vigorously for 2–3 minutes until smooth.
Fill the Cupcake Liners
Fill the cupcake liners two-thirds full with the batter. Be careful not to overfill.
Bake
Bake for 18–20 minutes, rotating the tins halfway through.
Check for doneness by inserting a toothpick into the center of a cupcake—it should come out clean.
Let the cupcakes cool in the tins for 10 minutes, then transfer them to a wire rack to cool completely.
Prep the Confectioners’ Sugar
Gently whisk the confectioners’ sugar in a large bowl to break up any clumps.
Cream the Butter
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium-high speed for 2–3 minutes, until light and fluffy.
Add Sugar and Liquids
Gradually add the confectioners’ sugar in two batches, beating on low speed after each addition. Scrape down the sides of the bowl.
Add the Kahlúa, heavy cream, vanilla extract, and kosher salt. Beat on medium-high speed for 3–4 minutes, until the frosting is smooth and fluffy.
Prepare for Piping
Scoop the frosting into a piping bag fitted with a large star tip.
Assemble the Cupcakes
Frost the Cupcakes
Pipe the frosting onto the cooled cupcakes in a swirl pattern. Start from the outer edge and work your way to the center.
Add Garnishes
Sprinkle the frosted cupcakes with chocolate shavings for an elegant finish.
Serve
Enjoy these delicious cupcakes immediately, or store them for later!