Make the bread dough. Warm milk in a small bowl in the microwave for about 30-45 seconds. Add 2 ¼ tsp active dry yeast and 1 tbsp sugar to the milk and gently whisk. Allow yeast to activate/bloom for 10 minutes, until puffy and bubbly.
While the yeast is blooming, combine flour, eggs, sugar, and salt in the bowl of a stand mixer fitted with the dough hook attachment. Then add yeast mixture.
Begin on low speed and gradually increase to medium speed as dough begins to form. Mix for about 5 minutes, then begin to add room temperature butter, one tablespoon at a time. Allow for 1-2 minutes in between adding each tablespoon of butter to ensure the butter is fully incorporated prior to adding the next (dough may temporarily break apart but will come back together when you continue to knead in the mixer).
After all of the butter is added, continue to knead dough for another 5 minutes in the mixer.
Lightly oil a large bowl and add dough. Cover with a towel or plastic wrap and allow dough to rise until it has doubled in size, about 1-2 hours.
Add nutella to a small bowl and add butter. Warm in the microwave for 20 seconds, until the butter is melted. Stir together and set aside.
Turn dough out onto a well floured surface. Cut dough into four equal pieces and roll each piece into a ball and set aside. Grab one of the dough balls and roll out into a large circle using a rolling pin. Repeat for all pieces.
Place a 9-inch plate on top of the dough and trace a circle, cutting off any extra pieces. Repeat for all four pieces to ensure that they are all the same size.
Assemble the Starbread
Place circle of dough on top of a parchment lined baking sheet. Add nutella/butter mixture to the top of the circle. Place another piece of dough on top and cover with raspberry preserves. Add the third piece of dough and nutella mixture. Place the last piece of dough on top.
Place a small cup in the middle of the dough. Then cut the dough into 4 quarters. (The best way to cut the dough is to use a pizza cutter, sharp knife, or dough scraper.) Then cut each quarter again to get 8 equal strips, and then 16. Grab two pieces of dough and twist inward three times and pinch the ends together to form the star point. Repeat for the remaining pieces.
Preheat the oven to 350 degrees F.Cover dough with a clean kitchen towel and allow to rise again for 20-30 minutes, until it becomes slightly puffy.
Make the egg wash by whisking together an egg and a tablespoon of water. Use a pastry brush to brush the top of the starbread with the egg wash.