Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking pan and line it with parchment paper.
Mix Wet Ingredients: In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth. Add eggs one at a time, then stir in vanilla extract and mashed potatoes.
Prepare Dry Ingredients: In a separate bowl, sift together the cocoa powder, instant coffee, baking powder, salt, and flour.
Combine & Fold in Chocolate Chips: Slowly add dry ingredients to the wet mixture, stirring gently until just combined. Fold in chocolate chips.
Bake the Brownies: Pour the batter into the prepared pan and spread evenly. Bake for 30-35 minutes or until a toothpick inserted in the center comes out with a few moist crumbs.
Cool & Serve: Let the brownies cool completely before slicing. Drizzle with melted chocolate for extra indulgence!