Preheat your oven to 350 degrees and line baking sheets with parchment paper.
In a medium bowl whisk together the flour, baking soda, and salt. Set aside.
In a large bowl beat together the butter with the sugars until it is light and fluffy, about 3 to 6 minutes.
One at a time add the eggs and then the vanilla extract. Make sure to scrape down the sides of the bowl as necessary.
Add all of the flour mixture and either fold it in with a spatula at first or turn on the mixer very low until it begins to combine, then turn the mixer on high and beat until just fully combined. Fold in 1 cup of the M&Ms.
Form the dough into balls using a 1 1/2 tablespoon cookie scoop. Place on the parchment lined baking sheets. Add 2 or 3 M&Ms to the top of each dough ball. Bake for 10 minutes or until the cookies begin to turn golden brown around the edges.
Allow to rest outside of the oven on the baking sheet for 2 minutes and then transfer to a cooling rack to cool completely. These are best when enjoyed after cooling. Store in an airtight container for up to one week.