Preheat the oven to 350°F (175°C) and line a 12-cup muffin tin with cupcake liners.

Cream together ½ cup of softened unsalted butter and ¾ cup of granulated sugar using an electric mixer until light and fluffy for about 2-3 minutes. Add in the eggs one at a time, followed by vanilla, espresso powder, and brewed espresso.

In a separate bowl, whisk together all-purpose flour, cocoa powder, baking powder, baking soda, and salt.

Gradually add the dry mixture to the wet mixture, stirring gently until just combined.

Scoop the batter into the lined muffin tin, filling each two-thirds full. Bake for 16-18 minutes or until a toothpick comes out clean.

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

For the frosting, beat ½ cup of unsalted butter until creamy, then gradually mix in 2½ cups of powdered sugar, espresso powder, and the remaining brewed espresso until light and spreadable.

Once cooled, frost the cupcakes with the espresso buttercream and optionally garnish with cocoa powder, chocolate shavings, or coffee beans.