Cream together softened butter, brown sugar, white sugar and 1 teaspoon vanilla extract with a stand mixer or hand mixer.

After 3-5 minutes the mixture should be lightened in color and appear fluffy.

Add in two eggs and an egg yolk, one at a time.

Then gradually add flour, baking soda and salt, until just combined.

Gently stir in chocolate chips and M&Ms.

Use a cookie scoop (or two spoons) to drop 1 tablespoon sized cookie dough balls onto cookie sheets (lined with parchment paper if not non-stick). Bake chocolate chip cookies for 10-11 minutes until edges are golden brown but centers are still soft. They will continue cooking as they cool on the baking sheet and wire cooling rack.

Repeat scooping and baking process for remaining cookies or freeze cookie dough for later (see below for instructions on how to freeze cookie dough).

Cool the cookies on the baking sheet for 3 minutes then transfer them to a wire cooling rack to continue cooling completely.