1. In the bowl of your stand mixer fitted with the dough hook, place the flour, brown sugar, and instant dry yeast. (If using active dry yeast, rehydrate it in the warm milk for 10 minutes.)
2. Mix on medium speed, then gradually add the warm milk, melted butter, and egg.
3. Continue kneading for 5 to 7 minutes until a smooth ball of dough forms.
4. Cover the dough with a towel and let it rise in a warm place for about 2 hours until it doubles in size. (Alternatively, you can let the dough rise in the fridge overnight.)
5. Punch down the dough on a lightly floured surface, then roll it out with a rolling pin into a rectangle about 12 x 16 inches (30 x 40 cm).
6. Spread the entire surface with Nutella, then roll the dough tightly from the long edge to form a log.
7. Using a knife or dental floss, cut the log into 12 equal pieces and place them in a large buttered baking dish, spacing them slightly apart to allow them to rise.
8. Cover again with a towel and let the dough rise a second time for 30 minutes to 1 hour.

Baking:

1. Preheat the oven to 350°F (180°C) and bake the rolls for about 20 to 25 minutes until they are golden on top.
2. Let the rolls cool slightly.

Nutella Cream Cheese Frosting:

1. In a medium bowl, place all the ingredients—cream cheese, softened butter, powdered sugar, vanilla, and Nutella.
2. Beat with an electric mixer for a few moments until the frosting is thick and creamy.
3. Spread the Nutella frosting over the rolls, sprinkle with chopped hazelnuts, and enjoy.