In a medium sized microwave safe bowl add the chocolate chips and sweetened condensed milk. Microwave 20 seconds at a time, stirring in between, until melted and smooth. Let cool until it’s not too hot to touch. (Can place in fridge for about 5 minutes.) Then line a baking sheet with wax paper and roll fudge into balls, about 1 Tbsp. Freeze for about 15 minutes while you make the cookie dough.

In the bowl of a stand mixer fitted with a paddle attachment, cream butter and brown and granulated sugar together on medium speed, beating until light and fluffy about 3 minutes. Add in egg and vanilla and mix until incorporated on low speed. Turn mixer up to medium-high and mix for 1 minute.

Scrape down the sides of the bowl if needed. Add the cornstarch, baking soda, and salt. Mix for 30 seconds then add the flour 1 cup at a time. Mix until fully incorporated.

Pull the fudge balls out of the freezer and wrap about 2 Tbsp. dough or as much as needed to completely wrap around the fudge. Place on baking sheet and repeat. Cover with plastic wrap and chill the dough for either 2 hours in the fridge or 15-20 minutes in the freezer.

When ready to bake, preheat oven to 350 F. Place cookie dough balls on 2 baking sheets lined with a silpat, or parchment paper, spaced 2 inches apart. Bake for 6 minutes remove from oven, top with M&M’s. Place cookie sheets back in oven, reversing positions for another 2-3 minutes or until edges are just golden.

Remove from oven, let cool on baking sheet for 5-10 minutes, and then transfer to wire rack to finish cooling. (Store in an airtight container.)