Preheat oven to 350°F (175°C). Grease an 8x8 inch baking pan.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time.
In a separate bowl, sift together the flour, cocoa powder, baking powder, and salt. Gradually add to the butter-sugar mixture, stirring until just combined. Stir in the coffee, chocolate chips, and walnuts.
Pour the batter into the prepared baking pan and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the brownies to cool completely before frosting.
In a medium bowl, combine the powdered sugar, melted butter, and coffee. Beat until light and fluffy. Spread over the cooled brownies.
Cut into squares and enjoy!
Interesting Facts
Mocha brownies were first created in the late 1800s in the United States.
The coffee flavor in the frosting helps to enhance the chocolate flavor of the brownies.
These brownies can be stored in an airtight container at room temperature for up to 5 days.