1. Preheat your oven to the temperature specified on your brownie mix box. Lightly grease and flour a 9×13 inch baking pan, or line it with parchment paper, leaving an overhang on the sides to easily lift the brownies out later.

2. In a large bowl, combine the brownie mix with the eggs, oil, and water (or whatever ingredients your specific box mix calls for). Stir until just combined; be careful not to overmix, as this can lead to tougher brownies. A few streaks of flour are fine.

3. Pour the prepared brownie batter evenly into your greased or lined baking pan. Place the pan in the preheated oven and bake for the time recommended on the brownie mix package, usually 25-30 minutes. The brownies are done when a toothpick inserted into the center comes out with moist crumbs, but not wet batter.

4. Once baked, remove the brownies from the oven and place the pan on a wire rack to cool completely. This step is crucial! Attempting to frost warm brownies will result in melted, messy frosting. Allow at least 30-60 minutes for them to cool down entirely.

5. While the brownies are cooling, prepare your frosting. In a medium bowl, whisk together the powdered sugar, milk, and vanilla extract until smooth and creamy. If the frosting is too thick, add a tiny bit more milk (1/2 teaspoon at a time) until it reaches a spreadable consistency. If it’s too thin, add a little more powdered sugar.

6. Once the brownies are completely cool, spread the vanilla frosting evenly over the top using an offset spatula or the back of a spoon. Immediately sprinkle with the red, blue, and white star sprinkles, arranging them in a festive pattern or scattering them randomly for a celebratory look.

7. Allow the frosting to set for about 10-15 minutes, if possible, before cutting the brownies into squares or bars. This helps prevent smudging the decorations. Use the parchment paper overhang to lift the entire brownie slab out of the pan for easier cutting.