Preheat oven to 375 degrees. Sift flour, corn starch, baking soda, and salt together in a large bowl. Set aside. Cream both sugars, butter, and Crisco together until light in color. Beat in eggs, one at at time. Mix in vanilla. Add flour mixture and mix until combined. Stir in mini chocolate chips and 1/2 cup M&Ms. Using a medium cookie scoop, (about 2 Tablespoons or 1/8 cups) drop cookies onto an ungreased cookie sheet, spacing about an inch apart. Gently push two to three M&Ms into the top of each cookie. Bake for 9-11 minutes. The cookies will not be set all the way and the edges will barely have started to turn golden brown if at all (the bottoms of the cookies may be brown though). Do not over bake! Let the cookies cool for three or four minutes, or until set, before removing to a wire rack to cool completely. Store in an airtight container. Enjoy!