In a small bowl, dissolve both packages of yeast in the warm water. Let it sit for a few minutes.
In a large bowl, combine the eggs, butter, sugar, salt, yeast mixture, and 3 cups of flour. Mix until well combined.
Add the remaining flour to form a very soft dough. Mix quickly but do not knead. The dough will be sticky. Cover with plastic wrap and refrigerate overnight.
The next morning, turn the dough onto a well-floured surface and divide it into two pieces. Shape each into a ball. Cover one with a tea towel to prevent drying while working on the other.
Using a rolling pin, roll one ball into an 18 by 12-inch rectangle. Spread with 1/4 cup of Nutella, leaving a 1/2-inch border, then sprinkle with 1/4 cup of ground almonds.
Roll the dough tightly from the long side, pinching the seam to seal. Place it seam side down on a cutting board. Slice into 12 pieces and arrange them in a well-oiled 13 by 9-inch baking pan. Cover with a tea towel and let rise in a warm spot for 1 hour.
Repeat this process with the second dough ball.
Preheat the oven to 375°F / 190°C and bake the rolls for 25 minutes.
While the rolls bake, prepare the glaze. Split the vanilla bean lengthwise and scrape out the seeds. In a small bowl, mix the icing sugar with the milk and vanilla bean seeds.
Once the rolls come out of the oven and are still warm, drizzle with the glaze. If desired, sprinkle with the chopped chocolate.