Preheat your oven to 350°F and line two baking sheets with parchment paper.
In a medium bowl, mix together the Nutella, flour, and egg until a soft dough forms. It might seem like it won't come together at first, but keep stirring—it will!
Roll the dough into 1-inch balls and place them about 2 inches apart on your prepared baking sheets.
Use a fork to gently press down on each cookie, creating a crisscross pattern (just like classic peanut butter cookies).
Bake for 8-10 minutes. The cookies should look set but still soft—don't overbake them or they'll lose that fudgy texture!
Let cool on the baking sheet for 5 minutes before transferring to a wire rack. Dust with powdered sugar if you want to make them extra festive!