Preheat the oven to 350F and prepare a 10-inch cast iron skillet with parchment paper.

Mix together the butter and sugar until light and fluff. Beat in the vanilla and eggs. Add in the flour, baking soda and salt on low speed. Hand mix in the chocolate chips and the M&M candies.

Press the dough into the prepared cast iron skillet. Bake for 15 minutes then cover with foil and continue baking for 15 minutes more.

Let cool for 30 minutes before slicing. Serve with a scoop of ice cream and a few more mini M&M's for garnish.