Preheat oven to 375 F. Line a cookie sheet with parchment paper or silplat mat.
Combine flour, baking powder, baking soda and salt in medium bowl; set aside.
Add butter, sugar and brown sugar to a large mixing bowl or stand mixer and beat well until creamed together.
Add egg and vanilla and mix until combined.
Gradually mix in the flour and mix until combined.
Stir in chocolate chips and m&m’s.
Scoop dough into large balls (about 3 Tablespoons) and place on prepared baking sheet about 2 inches apart.
Bake for 8 to 10 minutes or until light golden brown around the edges (Do not over bake.)
Let stand 1 minute on cookie sheet, then transfer to cooling rack to cool completely
Make ahead instructions: Prepare the cookie dough up to 5 days in advance and store in the refrigerator. Or make the cookies 1-2 days in advance.To freeze cookie dough: Scoop the cookie dough into dough balls and place them on a baking sheet. "Flash freeze" the dough by covering it loosely with plastic wrap and putting it in the freezer for 1 hour. Once the dough has hardened, move the dough balls to a freezer safe container and store for up to 3 months. Allow dough to thaw on the counter before baking.To freeze M&M cookies: Allow cookies to cool completely and store in a freezer safe container for up to 3 months.