Preheat the oven to 350° and line two cookie sheets with parchment paper. Do not use wax paper as it will burn in the oven.

Using a stand mixer, add the butter, powdered sugar, and vanilla. Stir well until fluffy.

In a small bowl, sift together the flour and salt.

Carefully tap in the flour 1 cup at a time, until all flour is in the mixture. This helps avoid a dust cloud and keeps you from getting flour all over the kitchen.

Mix until the dough comes together.

Add in the M&M's and fold in by hand until combined.

Using a small ice cream scoop, scoop balls of dough (about 2 tablespoons) and roll them in your hands to form a ball. Then place them on the prepared cookie sheet about 2" apart from each other.

Bake cookies for 8-10 minutes or until the bottoms are slightly brown.

Remove from the oven and place on cooling racks for just 5-10 minutes.

In a small bowl add your remaining powdered sugar, then roll each cookie in the sugar until coated on the outside.

Serve immediately and Enjoy! You can also store these in an airtight container for later or wrap for gift giving!