Preheat the oven to 350°F, and line a large baking sheet with parchment paper.
In a large bowl, use a hand mixer to combine butter, granulated sugar, and brown sugar. Beat on low speed until fluffy, about 3 minutes.
8 tablespoons unsalted butter, ½ cup granulated sugar, ¼ cup light brown sugar
Add the egg and vanilla until combined. Set aside.
1 teaspoon pure vanilla extract, 1 large egg
In a separate medium bowl, whisk together the flour, baking soda, cornstarch and salt. Pour the dry ingredients into the wet ingredients.
1 ½ cup all-purpose flour, 1 teaspoon baking soda, 1 teaspoon cornstarch, ¼ teaspoon kosher salt
Mix until ingredients are almost combined, a few flour streaks here and there are fine.
Stir in the M&Ms, and transfer the dough to the refrigerator for at least 30 minutes.
¾ cup plain M&Ms
Scoop 2 tablespoonfuls of dough onto the prepared baking sheet and space each at least 2 inches apart.
Bake for 10-12 minutes or until the cookies begin to set around the edges and appear soft in the center. Allow to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
Enjoy slightly warm or at room temperature. See post for storage options.
Notes
*The calories listed are an approximation based on the ingredients in the recipe card and a serving size of 1 cookie. Actual calories will vary.*For more information, tips, and answers to frequently asked questions, please refer to the post.*Photos courtesy of The Yummy Bowl.