Preheat the oven to 350°F.

In a large bowl, mix the brown sugar, white sugar, shortening, eggs, and vanilla with electric mixers on low speed until well mixed.

Add the 2½ cups flour, baking soda, and salt. Mix until just combined. Add the extra tablespoons of flour until the dough feels thick and almost dry to the touch. Stir the M&M's and chocolate chips into the dough.

Roll into large or small balls and place on a baking sheet,1-2 inches apart. Flatten slightly with your hand or with a wooden spoon. Press M&M's into the top of each cookie.

Bake for 8-10 minutes (they will be slightly under baked). DO NOT OVER BAKE! Cool on the cookie sheet for a few minutes and remove to a wire rack to cool completely.