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

Cream together softened unsalted butter and granulated sugar using an electric mixer on medium speed for about 2-3 minutes until light and fluffy.

Add room temperature eggs one at a time, followed by vanilla extract, instant espresso powder, and cooled brewed espresso, mixing until well incorporated.

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

Gradually fold the dry ingredients into the wet mixture using a rubber spatula until just combined.

Spoon the batter into prepared cupcake liners, filling them about two-thirds full. Bake for 16-18 minutes until a toothpick comes out clean.

Let the cupcakes cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.

While the cupcakes cool, beat softened butter until creamy. Gradually add powdered sugar, mixing on low speed.

Mix in instant espresso and brewed espresso until the frosting is light and fluffy.

Frost each cooled cupcake with espresso frosting using a piping bag or spatula.

Garnish with cocoa powder or chocolate shavings if desired.