Frosted Coffee Brownies

Ingredients

• 1/2 cup (1 stick) unsalted butter, melted
• 1 cup granulated sugar
• 2 large eggs
• 1 tsp vanilla extract
• 1/3 cup unsweetened cocoa powder
• 1/2 cup all-purpose flour
• 1/4 tsp salt
• 1/4 tsp baking powder
• 1 tbsp instant coffee granules
• 1/2 cup chopped walnuts (optional)
• For the Frosting:
• 1/4 cup unsalted butter, softened
• 1 1/2 cups powdered sugar
• 2 tbsp strong brewed coffee, cooled