Preheat oven to 350F.

Combine butter and sugar in a large bowl and use an electric mixer to beat until well-combined and light and fluffy (about 1 minute).

Add eggs, one at a time, beating well after each addition.

Stir in vanilla extract and food coloring, until well-combined.

Whisk together flour, cornstarch, baking powder, baking soda, and salt in a separate bowl.

Stir dry ingredients into butter mixture using a low-speed mixer, until well-incorporated.

Fold in M&M candies, then cover the bowl with plastic wrap and chill in the refrigerator for at least 30 minutes.

Drop cookie dough by heaping 1 ½ Tbsp-sized scoops onto a prepared cookie sheet lined with parchment paper.

Bake for 11-13 minutes, or until lightly golden, then gently press additional M&Ms into the tops of each cookie for decoration while they are still warm.

Allow cookies to cool completely on the cookie sheet before removing.