Line a 9 x13 baking pan with parchment paper. Set aside.
Combine flour, baking powder, baking soda and salt in a 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. Press dough into an even layer in prepared pan.
Bake for 18-25 minutes or until a toothpick inserted in the center comes out clean.
Remove from pan and let cool completely. Pull on side of parchment paper to remove bars from the pan and cut into squares.
Make ahead Instructions: The cookie dough can be made 2-3 days ahead of time, stored in the refrigerator.Freezing Instructions: allow baked bars to cool completely after cooking and cut them into squares. Place squares into a freezer safe bag or container and freeze for up to 3 months. Cookie dough can also be frozen for up to 3 months.Recipes Variations:
Add nuts: chopped walnuts or pecans
Substitute the chips: feel free to add or substitute your favorite "chips", like peanut butter or white chocolate chips.