• Dissolve the fresh yeast in the milk. In a medium-sized bowl mix well the butter with flour and salt. Add the eggs and the milk with yeast and mix until well blended. Knead well, cover with plastic, and refrigerate for about 1 hour to let the yeast develop. 

Prepare the spinach filling.

• In a saucepan, put water to boil, wait until the water is to a bubbling boil, add fresh spinach, and cook for 3 minutes then drain immediately. 
• Set aside to cool down. When cold enough cut a little bit in smaller pieces.
• In a large flat-bottomed frying pan heat oil over medium-high heat. Cook onion and garlic for about 5 minutes until soft. Add the mushrooms and spinach and cook until any liquid has evaporated. Add salt and pepper and remove from the heat and allow to cool.
• Preheat the oven to 180 (350F).

How to shape the pinwheels.

• Cut the dough into 3 equal pieces. Sprinkle flour on the working surface. Using a rolling pin roll out each piece into a rectangular about 12 inches (30 cm) long, 10 high.
• Cover the dough with 1/3 of the spinach filling. Roll and cut into 1 inch slices. Arrange dough pieces in a baking tray. Brush with egg yolk. 
• Bake for about 25-30 minutes or until nicely browned.