Preheat oven to 350.
Line a 9x13 Pan with parchment paper or spray with cooking spray.
Heat butter and brown sugar in a medium sized saucepan, stirring constantly until smooth.
Cool for 5 minutes.
Add Eggs one at a time. Stir until incorporated.
Add Vanilla.
Add Flour, Salt, Baking Soda and Baking powder and stir until combined.
Add half of the chocolate chips and M&M's and stir
Transfer mixture to prepared pan.
Top with remaining M&M's and chocolate chips.
Bake for 25-30 minutes.
Allow to cool until slightly warm.
Remove from pan and cut into bars