Preheat the oven to 350º F. Line a cookie sheet with a silicone baking mat or parchment paper.

In a mixing bowl combine the flour, cornstarch, baking soda, and salt. Set aside.

In a larger mixing bowl combine the butter, brown sugar, and granulated sugar. Beat on medium speed for 1 minute. You want this mixture to be fluffy and pale in color.

Add in the eggs and vanilla extract, beat for 30 seconds.

Gradually mix in the dry ingredients, mixing on low speed. The dough will be thick. Use a spatula to hand mix in 1 cup of M&Ms. The other cup of M&Ms I use to press on the outside of the dough balls.

Use a cookie scoop to form golf ball sized cookie dough balls, roll into a smooth ball between your hands. Press the remaining 1 cup of M&Ms on the outside of the dough balls. I like to load mine with M&Ms! Place about 8 cookies on a cookie sheet lined with a silicone baking mat at a time. I recommend only baking 1 cookie sheet at a time for even baking.

For the cookies in the photos, the dough balls were about 3 heaping tablespoons (golf ball sized), so that’s a large cookie! I baked those for 13-16 minutes – just until the edges of the cookies would begin to firm up and brown slightly. The result is a soft and chewy cookie! If you make smaller dough balls, you should reduce the baking time to 12-14 minutes since the baking estimates are for golf ball sized dough balls.

Allow the cookies to cool for 15 minutes on the baking sheet before removing. Make sure the baking sheet is cool before adding more dough balls and returning to the oven. Using 2 baking sheets allows one to cool while the other is in the oven.