Whisk together the flour, baking soda, and salt in a medium sized bowl. Set aside.
Combine the two sugars and butter in the bowl of an electric mixer.
Mix on low until fully incorporated and fluffy, about 2 minutes.
Stir in your eggs and vanilla until combined with the butter, 30 seconds should do it.
Add the dry ingredients to the bowl of wet ingredients.
Mix until your dough starts to form, 1 to 2 minutes.
Fold in 3/4 cups of the m&m candies.
Scoop the dough into 1/4 cup full. Roll and place onto a parchment lined tray.
Chill dough for at least 30 minutes or up to 3 days.
Preheat the oven to 350 degrees and line cookie sheets with parchment paper.
Place the dough rounds 2 inches apart on the prepared baking trays.
Press additional candies onto the tops of each cookie if desired.
Bake 12-15 minutes or just until the edges start to lightly brown.
Cool for 10 minutes on the baking tray.