Preheat your oven to 325°F. Line rimmed baking sheets with unbleached parchment paper and set them aside.

In a large bowl, place the oat flour, oats, baking soda, salt, cocoa powder, and granulated sugar, and whisk and/or mix until well-combined.

Create a well in the center of the dry ingredients, and add the butter, Nutella, eggs, and vanilla, and mix until combined. The cookie dough will be very thick and relatively stiff.

Press the mixture down with the back of the mixing spoon to help the cookie dough absorb all of the dry ingredients. Add the M&Ms and chocolate chips, and mix until they’re evenly distributed throughout the cookie dough.

Using a spring-loaded ice cream scoop or two spoons, scoop the dough into mounds about 2 1/2 tablespoons each on the prepared baking sheets, about 2 inches apart from one another.

Using wet fingers, press each mound down into a disk about 1/2-inch thick.

For thicker cookies, chill in the refrigerator for about 30 minutes or the freezer for about 5 minutes.

Place the baking sheets, one at a time, in the center of the preheated oven and bake until just set in the center (10 to 12 minutes).

Remove from the oven and allow to cool on the baking sheet until firm before transferring to a wire rack to cool completely.