Preheat your oven to the recommended temperature for baking brownies. Prepare your baking pan by lightly greasing or lining with parchment paper.

In a mixing bowl, combine the stick of unsalted butter and granulated sugar. Blend until fluffy and slightly paler in color.

Add the two large eggs to the mixture and mix until fully incorporated, achieving a smooth batter.

Stir in the vanilla extract and coffee extract or instant coffee.

Gradually sift in cocoa powder, flour, salt, and baking powder. Mix until just combined.

Incorporate the instant coffee granules into the batter, mixing until evenly distributed.

Pour the brownie batter into the prepared baking pan and smooth the top with a spatula.

Bake the brownies until set and edges pull slightly away from the sides of the pan.

Remove from oven and cool in the pan for a few minutes, then transfer to a wire rack to cool completely.

Melt the unsalted butter for the frosting in a bowl. Gradually add the powdered sugar and mix until combined.

Add heavy whipping cream to reach desired frosting consistency.

Once brownies are cool, spread the frosting evenly on top.

Allow the frosting to set slightly before cutting into squares or rectangles.