To make the pasta:

Cup of Yum
1. In a large bowl, combine the flour and salt.
2. Mix in the eggs and slowly add just enough water to form a soft dough.
3. On a lightly floured surface, knead until smooth. If still too crumbly to come together, add a little more water. If too sticky to handle, add a little more flour.
4. Cover with a towel or plastic wrap and set aside at room temperature for 30 minutes.

To form the filling:

1. Bring a large pot of water to a boil. Add the spinach and cook just until blanched, about 1 minute.
2. Drain and set aside to cool slightly. Once cool enough to handle, squeeze excess water out of the leaves and finely chop.
3. Chop the rolls into small cubes and place in a medium bowl. Add the milk and allow the bread to soak while you prepare the rest of the filling.
4. In a large skillet, melt the butter over medium heat. Add the onion and cook, stirring occasionally, until softened.
5. Stir in the garlic and cook until just fragrant, 30 seconds to 1 minute. Remove from heat and allow to cool slightly.
6. In a large bowl, combine the beef or pork, crumbled bratwurst, parsley, salt, pepper, and nutmeg.
7. Add the finely chopped spinach and the cooled onion garlic mixture.
8. Squeeze the milk from the cubes of bread and crumble into the bowl.
9. Add the eggs and combine to create an evenly distributed filling.

To form the Maultaschen:

1. In a small bowl, whisk together the egg yolk and water.
2. Divide the dough into four equal pieces.
3. Place one piece on a floured work surface and cover the remainder. Line a large baking sheet with parchment.
4. Roll the dough into a thin sheet using a pasta machine or rolling pin, until it is about 1/16th inch (1.5 millimeter) thick.
5. To form individual squares: Cut the sheet of pasta into 3-4 inch (7.5-10 centimeter) squares.
6. Place a spoonful of the pork and spinach filling in the center of the square, leaving about 1/4-1/2 inch (6-12.5 millimeters) free around the edges.
7. Brush the edges with the beaten egg wash and fold the square of pasta over, sealing the edges.
8. If desired, press a fork around the edges to seal well. Place on the parchment-lined baking sheet and repeat with remaining dough and filling.
9. To form strudel-like Maultaschen: After rolling the dough into a thin sheet, spread the filling lengthwise across the sheet, leaving about 1-2 inches (2.5-5 centimeters) free on each side.
10. Brush the free edges with the egg wash and roll up the dough tightly, long side to long side, pressing out any air.
11. Use a wooden handle to press down on the roll of dough and create dumplings, about 2 inches (5 centimeters) apart. Cut along the separated, pressed down edges to form the individual Maultaschen and arrange in a single layer on the parchment-lined baking sheet.
12. Repeat with remaining dough and filling.
13. Bring a large pot of salted water to a boil. Reduce heat to a light simmer and cook the Maultaschen, a few at a time to not overcrowd, until floating on the top and cooked through, about 10 minutes.
14. Serve in broth with fresh herbs or slice and pan-fry in butter with caramelized onions.