Preheat & Prepare the Baking Pan:
Preheat your oven to 350°F (175°C).
Grease a 9x13-inch baking pan or line it with parchment paper.
Make the Brownie Batter:
In a large mixing bowl, whisk together melted butter, granulated sugar, and brown sugar until smooth.
Add eggs, vanilla extract, and brewed coffee. Whisk until well combined.
Sift in the cocoa powder, flour, salt, and baking powder. Stir gently until just incorporated.
Fold in chocolate chips, if using.
Bake the Brownies:
Pour the batter into the prepared pan, spreading it evenly.
Bake for 30-35 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
Let the brownies cool completely before frosting.
Prepare the Coffee Frosting:
In a mixing bowl, beat the softened butter until creamy.
Gradually add powdered sugar, beating until fluffy.
Mix in brewed coffee, vanilla extract, and espresso powder (if using). Beat until smooth and spreadable.
Frost the Brownies:
Spread the coffee frosting evenly over the cooled brownies.
Slice into squares and enjoy!