In a medium-sized mixing bowl, add 1 cup unsalted butter, ¾ cup brown sugar, and 1 cup granulated sugar. Using an electric hand mixer, mix until light and fluffy, about 2 minutes.
Mix in 2 large eggs and 2 teaspoons vanilla extract.
Add in 3 ½ cups all-purpose flour, 1 teaspoon baking soda, and 1 teaspoon salt. Mix until combined.
Stir in 1 cup chocolate chips and 1 cup M&Ms.
Using a 1-inch cookie scoop, scoop the dough onto the prepared baking sheet. Add additional M&Ms on top of the dough if desired. Bake for 8 minutes or until almost set through the center.
Remove from the oven and let cool for several minutes before transferring to a cooling rack to cool.