Preheat your oven to 350°F (175°C). Line your sheet pan with parchment paper, leaving some overhang on the sides for easy removal later.
In a large saucepan over low heat, melt the butter along with the unsweetened chocolate. Stir frequently until smooth and fully melted. Remove from heat and allow it to cool slightly.
In a separate mixing bowl, whisk together the eggs, instant coffee, and vanilla extract until well combined. Gradually add in the sugar, mixing until smooth and slightly lighter in color.
Once your chocolate mixture has cooled slightly, slowly pour it into the egg and sugar mixture, stirring constantly to prevent the eggs from cooking. Mix until fully incorporated.
In another bowl, whisk together the flour, baking powder, and salt. Gradually add this dry mixture to the wet ingredients, folding gently until just combined. Be careful not to overmix.
Gently fold in the semisweet chocolate chips, ensuring they are evenly distributed throughout the batter.
Pour the brownie batter into the prepared sheet pan, spreading it out evenly. Bake for 25-30 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.
Once baked, remove the brownies from the oven and allow them to cool in the pan for about 15 minutes. Use the parchment overhang to lift them out onto a wire rack to cool completely before slicing into squares.
