Preheat oven to 375° F. If using convection, preheat to 375 as well.
Cut butter into pieces ( about 2 tablespoons each) and place in mixing bowl. I use a Kitchen Aid and power it on 2 (low).
After a few seconds, add granulated sugar, brown sugar and vanilla extract. Mix on low speed until creamy (this takes just a few seconds). The butter and the sugars should be mixed enough so no chunks of butter are visible.
Using a spatula, scrape down the sides and bottom of the bowl to insure all ingredients are incorporated.
Dump 2 3/4 cups of the flour, soda, salt, chocolate chips and all M&M's (reserving 3/4 cup for top!) into bowl with butter mixture. Mix on low for a few seconds. I like to use a pulsing action (turn mixer off and on quickly for a few seconds).
Turn the dough with a rubber spatula so the bottom of the dough is mixed into the top of the dough. This will insure the flour is mixed in properly and the candy and chips are distributed evenly.
If the dough is sticky or wet looking, sprinkle in an additional 2 tablespoons of flour to the dough. Fold into dough by hand using a spatula.
Using a cookie scoop, drop onto un-greasedbaking sheets, or baking sheets lined with parchment paper. Place 6-8 scoops of dough on each baking sheet.
If using convection, bake for 7-10 minutes until golden brown.
If using regular (non convection) oven, bake at 375 for 10-12 minutes.
Cookies should be slightly golden and the cookie should not be wet or shiny on top. While cookies are still warm, press a few M&M 's into the top of the cookies after baking for best results.