Chocolate Mint Cupcakes

Preheat oven to 350u0b0F and line two 12-cup mini muffin pans with baking cups.
In a small bowl, whisk together boiling water and cocoa, then set aside to cool completely.
Beat sugar, butter and peppermint extract in a large mixer bowl at medium speed until well blended (about 3 minutes). Add eggs and beat well. Set aside.
Whisk together flour, baking soda, baking powder and salt in a medium bowl. Add half of flour mixture to the sugar mixture and beat until just combined. Add cocoa mixture, then finish by adding the remaining flour mixture.
Fill each baking cup with a slightly rounded tablespoon of batter, to about 1/4 inch below the top of the liner. Bake until a toothpick inserted in the center comes out clean, about 12 to 15 minutes. Cool the cupcakes for 2 minutes in the pan on a wire rack. Then holding an edge of each liner, carefully lift the cupcakes from the pan and place them on the wire rack to cool completely before frosting.
To make buttercream frosting, beat butter in a large mixer bowl on medium speed until light and fluffy. Reduce speed to low; add powdered sugar and beat until smooth. Add peppermint extract and beat on medium speed until airy. Fit a pastry bag with a large French tip and fill the bag with the buttercream. Then pipe a spiral onto the top of each cupcake.
Store leftover cupcakes in an airtight container in the refrigerator up to 3 days. Bring to room temperature before serving.