Creating Espresso Brownie Cupcakes with Coffee Buttercream is an enjoyable process. Follow these simple steps to make your delicious cupcakes:

For the Brownie Cupcakes:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners.
2. Melt Butter: In a saucepan, melt the butter over low heat. Remove from heat and stir in the granulated sugar until well combined.
3. Add Eggs and Vanilla: Whisk in the eggs, one at a time, followed by the vanilla extract until fully incorporated.
4. Mix Dry Ingredients: In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt.
5. Combine Mixtures: Gradually fold the dry ingredients into the butter and egg mixture until just combined. Avoid overmixing.
6. Add Espresso: Gently mix in the cooled brewed espresso until evenly distributed.
7. Fill Muffin Tin: Pour batter into prepared muffin tins, filling each cup about 2/3 full.
8. Bake: Bake in the preheated oven for 20-25 minutes or until a toothpick inserted in the center comes out clean.
9. Cool: Remove from the oven and allow cupcakes to cool in the tin for about 10 minutes before transferring to a wire rack to cool completely.

For the Coffee Buttercream:

1. Beat Butter: In a mixing bowl, beat the softened butter until creamy using an electric mixer.
2. Add Powdered Sugar: Gradually add the powdered sugar, mixing on low speed to avoid a sugar cloud until incorporated.
3. Mix in Espresso: Add the cooled brewed espresso, milk, and vanilla extract. Increase the speed to medium and beat until the frosting is fluffy and smooth.
4. Adjust Consistency: If the frosting is too thick, add a little more milk. If too thin, add more powdered sugar.