Preheat your oven to 350°F (175°C), grease the cookie sheet, or line a baking sheet with parchment paper.
In a large mixing bowl, combine a cup of Nutella, an egg, and flour. Stir well until you have a smooth and homogenous mixture.
Take small portions of the dough and roll them into 1-inch balls. Place the balls on the prepared baking sheet, leaving some space between each cookie.
Using a fork, gently press down on each cookie ball to create a crisscross pattern.
Bake the cookies for 12-15 minutes or until the edges are set but the centers are still soft. Remember that cookies will firm up as they cool.
Allow the cookies to cool on the baking sheet for a few minutes before transferring them to a wire cooling rack to cool completely. Once cooled, you can add frosting if desired.
Enjoy the goodness of these 3-ingredient Nutella cookies!