Preheat the oven to 350°F. You are more than welcome to use a handheld mixer or a stand mixer with a paddle attachment.
In the stand mixer, cream the butter and the sugars together until nice and smooth.
Add the egg and pure vanilla extract, mix for about a minute again on medium-low speed.
Gradually add the flour, baking soda, pinch of salt, and mix on medium low speed until a tacky dough forms.
Mix or fold in the m and m's and take a spoon or an ice-cream scoop and scoop out 24 small cookies onto a baking sheet lined with parchment paper. You can also make 12 large cookies as well but the baking time may increase.
Bake for 12 minutes or until the edges are golden.