Instructions:

• Preheat oven to 350 degrees.
• Line cookie sheets with parchment paper.
• Add flour, baking soda, and cornstarch in a medium bowl.
• Mix to combine. Set aside.
• Using your electric mixer add butter and both sugars.
• Cream together until smooth and without lumps.
• While mixer is on, slowly add the egg, egg yolk, and vanilla. Mix well.
• Slowly add the flour mixture, stirring until completely mixed.
• Stir in the M&Ms and sprinkle. Stir just to combine.
• Transfer cookie dough to the refrigerator. Chill for 30 minutes.
• Measure cookie dough with a tablespoon placing the dough on the prepared cookie sheet.
• Bake at 350 degrees for 10-12 minutes.
• Check that the cookie edges are slightly brown.
• The cookie centers will be soft and puffy.
• Allow the cookies to cool slightly on the cookie sheets before transferring them to a wire rack to cool completely.
• Makes 24 cookies