Preheat your oven to 350°F (175°C) and line a cupcake tin with paper liners.

In a large mixing bowl, whisk together all-purpose flour, granulated sugar, light brown sugar, unsweetened cocoa powder, Dutch-process cocoa powder, baking powder, baking soda, and salt until well combined.

In a separate bowl, crack in the large eggs, then add buttermilk, vegetable oil, and vanilla extract. Whisk until smooth.

Dissolve the espresso powder in hot water and add to the wet ingredients, mixing well.

Pour the dry ingredients into the wet ingredients, stirring gently to combine.

Spoon the batter into the cupcake liners, filling each about two-thirds full.

Bake for 18-20 minutes, checking for doneness with a toothpick.

Let cupcakes cool for 5 minutes in the tin before transferring to a wire rack to cool completely.

For the ganache, heat heavy whipping cream and pour it over chopped Andes mints, whisk until smooth.

Beat the unsalted butter until creamy, gradually add sifted powdered sugar and peppermint extract, mixing until fluffy. Add heavy cream and crushed chocolate wafers until well combined.

Once cooled, core a portion from the top of each cupcake, fill with ganache, replace tops, then pipe mint buttercream frosting generously on top.