In a stand mixer, combine 1 cup of softened unsalted butter, ¾ cup of light brown sugar, and ¾ cup of granulated sugar. Beat on medium speed for about 2 minutes until the mixture becomes light and fluffy.

Add 1 large egg and 1 teaspoon of vanilla extract to the creamed mixture. Mix on low speed until well combined.

In a separate bowl, whisk together 2 ¼ cups of all-purpose flour, 1 teaspoon of cornstarch, 1 teaspoon of baking soda, and ½ teaspoon of salt. Gradually add this dry mix to the wet ingredients, stirring on low speed until combined.

Gently fold in 1 ½ cups of red, white, and blue M&M’s.

Scoop golf-ball-sized portions of cookie dough onto a lined baking sheet, spacing them about 2 inches apart. Press a few extra M&M’s on top for decoration. Cover and chill the dough for 30 minutes.

Preheat your oven to 350°F (175°C).

Once the dough has chilled, place the baking sheet in the preheated oven and bake for 10-11 minutes.

Let the cookies cool on the baking sheet for about 5 minutes before transferring to a wire rack to cool completely.