Measure milk into a liquid measuring cup and butter. Microwave for 1 minute and mix until butter melts completely and is 110-120 degrees F.
In the bowl of a stand mixer fitted with the paddle attachment, combine the milk mixture, yeast, and about 1 tablespoon of the sugar. Cover with a towel and let the yeast activate for 5 minutes.
Mix in the egg yolks, remaining sugar, and salt. Add 2 1/2 cups flour and mix until combined. Switch to a dough hook, add the remaining 1/2 cup flour and knead for 5 minutes on medium until a soft smooth dough forms.
Grease a mixing bowl with cooking spray and place the dough inside. Flip it over so that the top of the dough is greased. Cover bowl with a clean towel and let it rise until about double in bulk (50-60 minutes).
Preheat oven to 375 degrees F and grease a muffin tin.
Divide dough in two. Roll one half out into a 14x10 inch rectangle. Heat Nutella up in the microwave for a about 20 seconds so it's a little thinner and then spread it over the dough within 1/4 inch of the sides. Sprinkle on the hazelnuts.
Roll out the remaining dough into another 14x10 inch rectangle and place on top of the filling. Press the edges together to seal and then cut into 12 (14-inch) strips. This works best using a pizza cutter and cutting the dough into 4 long strips and then cutting each of those into 3 strips.
Take each strip and twist it into a coil (about 7 twists). Spiral each twist down into the muffin cup and tucking the end down into the middle.
Mix the egg white with 1 tablespoon water and then brush over the tops of the twists. Bake for 14-16 minutes until golden brown. Immediately remove from muffin cups and place on cooling rack. Cool for 5 minutes, dust with powdered sugar, and serve warm.