A vanilla cupcake spiked with boozy homemade Irish cream and finished with a decadent chocolate buttercream frosting is the pinnacle of St. Patrick's Day treats!
Sift together 1½ cups (180g) flour, 1 teaspoon espresso powder, 1 teaspoon baking powder, and ½ teaspoon kosher salt in a medium bowl. Set aside.
Prepare the wet ingredients:
Combine ½ cup (113g) butter and 1 cup (200g) light brown sugar in a large bowl. Beat with an electric mixer until combined.
Add 2 eggs and beat for 2 minutes until smooth. Add ½ cup (120g) sour cream, 1 teaspoon vanilla extract, and ½ cup (120ml) Irish cream. Continue mixing until completely smooth.
Add the dry ingredients to the batter:
Add the bowl of dry ingredients to the batter and beat with an electric mixer at medium speed until combined, being careful not to overwork the flour.
Bake the cupcakes:
Use a cookie scoop to spoon the batter into the liners, filling each one up about ⅔ of the way full. Transfer to the oven for 20 to 23 minutes or until a toothpick inserted into the cupcake comes out clean.
Transfer the cupcakes to a wire rack to cool completely, at least 1 hour.
Make the chocolate buttercream frosting:
Sift 3½ cups (420g) powdered sugar and ½ cup (60g) cocoa powder into a large bowl. Add ½ cup (113g) butter, 6 tablespoons (90g) heavy cream, and 1 teaspoon vanilla extract. Beat with an electric mixer until smooth, being careful not to overmix. Add another 1 to 2 tablespoons (15g to 30g) heavy cream if needed for the frosting to reach a thick, smooth, creamy consistency.
Frost the cupcakes:
Transfer the frosting to a piping bag fitted with a star tip. Pipe the frosting onto each cupcake.
To serve:
Sprinkle the cupcakes with festive St. Patrick’s Day sprinkles and enjoy!