Cream 1 cup of softened unsalted butter, 1 cup of light brown sugar, and 1/2 cup of granulated sugar together on medium speed for about 2 minutes until light and fluffy.

Mix in 1 large egg and 2 teaspoons of vanilla extract until well incorporated, usually about 30 seconds.

In a separate bowl, whisk together 2 ½ cups of all-purpose flour, 1 teaspoon of baking soda, 1 teaspoon of salt, and 1 tablespoon of cornstarch. Gradually add this mixture to the wet ingredients.

Fold in 1 ½ cups of red, white, and blue M&Ms into the cookie dough until evenly distributed.

Scoop golf-ball-sized portions of dough onto lined baking sheets, leaving about 2 inches of space between them. Press a few extra M&Ms on top for decoration.

Cover with plastic wrap and chill the cookie dough in the refrigerator for at least 30 minutes.

Preheat your oven to 350°F (175°C). Bake the cookies for 10-11 minutes until the edges are set but the tops look slightly underbaked.

Let the cookies cool on the baking sheet for about 5 minutes, then transfer to a wire rack to cool completely.