Preheat oven to 350 degrees and line your baking sheet with parchment paper or a silicone mat.
In a large bowl or mixer, cream together butter and sugars for atleast 1 - 2 minutes. Beat in the egg and vanilla. Mix until combined.
Add in your dry ingredients; flour, baking soda, and salt. Mix unti dough forms.
Fold in the chocolate chips and the M&M candies.
Drop by rounded tablespoonfuls or using a cookie scoop place dough at-least 2 inches apart on your lined cookie sheet. Top each cookie with a couple extra M&M's (if desired).
Bake for 10 minutes or until the edges of your cookie start to turn golden brown. Don't overbake or you will loose some of the chewyness.
For a gluten free cookie substitute a gluten free flour mix.
Prepare the dough and refridgerate as is, or drop in balls on a baking sheet an freeze. Once frozen store in an airtight container. When ready to enjoy place frozen dough on a cookie sheet and follow the original baking instructions.
Higher Temp Trick
You can bake these cookies at 375 F. The result will be a chewyier cookie. The outside will brown slighty faster. So, if you love a super chewy cookie...this is for you!
The Best Chocolate Chip M&M Cookies https://afewshortcuts.com/best-mm-chocolate-chip-cookies/