Measure milk into a liquid measuring cup and add 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°F and grease a muffin tin.
Divide dough in two. Roll one half out into a 14 x 10 inch rectangle. Heat Nutella up in the microwave for 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 14 x 10 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 tuck 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.