Cream the butter, both sugars, shortening, vanilla for about 5 minutes until light and fluffy. Stop the mixer and scrape well.

Add the eggs one at a time, mix well between additions.

Scrape well.

Sift all the dry ingredients together and dump the dry ingredients into the mixing bowl, while the mixer is on the lowest setting. Mix until just combined. Fold in the rest of the dry ingredients with a rubber spatula.

Portion out the cookie dough with an ice cream scoop onto a lined cookie sheet. Freeze the extra dough in a storage bag. Leave the rest of the dough balls on the sheet and freeze for 15 minutes, while you preheat the oven to 400°F.

After 15 minutes, bring out the cookies on the sheet and roll them slightly between  your palms.

Dip them into the M&M's and flatten them with your fingers slightly. Place the sheet in the oven and instantly turn down the temperature to 350°F.

Bake for 10-15 minutes. Watch the cookies closely. They should have slightly golden edges, but should look slightly under-cooked.

Let them continue to cook on the sheet out of the oven for about five minutes, before moving them to a wire rack to cool.

Store in a container that's covered for about a week. Freeze any leftovers.