Using a stand mixer, combine the nutella and brown sugar for about a minute. Add the eggs and vanilla and beat until combined. Add the whole oats, quick oats, and salt and mix on low until fully incorporated. By hand, stir in the M&Ms and white chocolate chips until evenly dispersed throughout the dough. Place cookie dough in the refrigerator for at least 4 hours, or overnight.

Shape the cookie dough into balls about the size of a golfball and place on prepared baking sheet 2 inches apart. Bake for 13-15 minutes, until the edges have set and the centers have puffed up and started to crackle. They may look underdone, but try not to overbake these cookies or else they won't retain their chewy texture. They will deflate as they cool.

Allow cookies to cool on baking sheets for ten minutes before transferring to a wire rack to cool completely. Store cookies in an airtight container.