In a large mixing bowl with a hand held beater beat the softened butter, white and brown sugars until light and fluffy.

Add the egg and vanilla extract to the bowl and beat for 3 minutes.

Gradually beat the dry ingredients into the butter and sugar mixture. If the cookie batter is too thick for the hand beater switch to a wooden spoon and stir the flour mixture into the dough until completely combined. Scrape the bottom of the bowl well to bring any flour up into the batter. Mix until there are no streaks of flour visible.

Fold 1 cup of red and green M&M's into the cookie batter until the candy pieces are evenly distributed through out the cookie dough.

If the cookie is extremely soft cover the bowl and refrigerate 30 minutes to allow the dough to firm up. Well chilled cookie dough is best or the soft dough may spread too much as it bakes and you will have flat thin cookies.

Use a 2 inch dough scoop to scoop the cookie dough. Drop each scoop of cookie dough 2 inches apart on a parchment paper lined cookie sheet. Press 5 red and green M&M's onto the top of each of the cookie dough balls on the baking tray.

Bake the cookies in the preheated oven for 8 to 10 minutes or until golden around the edges.

Remove the tray from the oven when the cookies are done. Allow the cookies to cool for 5 minutes on the baking tray before transferring the cookies to a wire cooling rack to finish cooling.