Line 2 large baking sheets with parchment paper. In a large bowl, whisk together the flour, baking powder, baking soda and salt.

Using a mixer, cream the butter, sugar and brown sugar on high speed, until light and fluffy. Add in the eggs; scrape down the sides of the bowl.

Slowly add the flour and vanilla until combined. Mix in the M&M candy pieces (and walnuts) by hand.

Using a small ice cream scoop, place the cookie dough on the parchment paper.

Bake at 350 degrees F for 8-10 minutes. Allow to cool for several minutes before serving.