Start by brewing 4 ounces of coffee and then place it in the refrigerator to cool.
Preheat your oven to 350 degrees.
In a large bowl, combine the melted butter and sugar. Mix in the eggs one at a time, followed by the vanilla extract and the cooled dark coffee.
Add in the unsweetened cocoa powder, all-purpose flour, and salt. Mix everything together until you have a smooth batter. Pour this batter into a 9×13-inch baking dish lined with parchment paper. Smooth out the top.
Place the baking dish in the preheated oven and bake for 25-30 minutes or until a toothpick inserted into the center comes out clean. Allow the brownies to cool for about 20-25 minutes before frosting.
To make the chocolate icing, in a large bowl, use a hand mixer to combine the softened butter, ¼ cup of milk, cocoa powder, and vanilla extract. Start mixing on low speed and gradually increase it until the mixture is smooth.
Add in the powdered sugar and continue mixing until there are no more lumps. If the frosting is too thick, you can add more milk to reach your desired consistency.
Once the brownies have cooled, spread the chocolate icing evenly over the top.
Cut the brownies into squares and enjoy your delicious homemade brownies!