Preheat oven to 375 and line cookie sheets with parchment paper. In a stand mixer, cream shortnening, sugars, eggs, and vanilla thoroughly. Add dry ingredients gradually to creamed mixture, mixing well. Fold in ½ cup M&Ms, reserve remaining M&Ms for decorating. Drop by teaspoon (or melon baller) onto baking sheet. Decorate tops of cookies with remaining M&Ms - I do about 3 per cookie on top. Bake 10 to 12 mins or until golden brown. Makes 6 dozen 2½ in cookies.
Recipe by Five Wooden Spoons at https://www.fivewoodenspoons.com/2012/12/21/aunt-sallys-mm-cookies/