Step 1

Using a hand mixer or a stand mixer fitted with paddle attachment, cream the softened butter and both sugars together on medium speed until smooth. Add the egg and mix on high until combined, about 1 minute. Scrape down the sides and bottom of the bowl as needed. Add the vanilla and molasses and mix on high until combined. Set aside.

Step 2

In a separate bowl, toss the oats, flour, cinnamon, baking soda, and salt together. Add to the wet ingredients and mix on low until combined. Fold in the add-ins. Dough will be thick. Chill the dough for at least 30 minutes in the refrigerator.

Step 3

Preheat oven to 325°F (163°C). Line two large baking sheets with parchment paper or silicone baking mats.

Step 4

Roll balls of dough (about 1.5 tablespoons of dough per cookie) and place 2 inches apart on the baking sheets. I pressed a few extra M&Ms into the tops of the cookies for looks. Bake for 10-11 minutes until very lightly browned on the sides. The centers will look very soft. Remove from the oven and let cool on baking sheet for 5 minutes before transferring to a wire rack to cool completely.