Preheat your oven to 350°F (175°C) and prepare an 8-inch baking dish by coating it with non-stick spray or lining it with parchment paper, followed by a light spray of non-stick spray.
In a microwave-safe bowl, melt the butter in the microwave. Once melted, transfer the butter to a large mixing bowl.
To the bowl with the butter, add the sugar, eggs, and vanilla extract, stirring until everything is thoroughly blended.
Gradually add the flour, cocoa powder, salt, and baking powder to the wet ingredients, and mix until the batter is smooth and fully combined.
Spread the batter evenly into the prepared baking dish and place it in the oven. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Allow the brownies to cool completely before starting on the frosting.
For the frosting, dissolve the instant coffee granules in the heavy whipping cream and set aside.
In a separate bowl, beat the unsalted butter until it becomes light and fluffy. Gradually add the powdered sugar, mixing until fully combined.
Slowly pour in 2 tablespoons of the coffee-infused cream and mix well. If needed, continue adding more cream, 1 tablespoon at a time, until the frosting reaches your preferred consistency.
Once the frosting is ready, generously spread it over the cooled brownies. Slice and serve to enjoy!