In a large mixing bowl, combine the flour, eggs, and a pinch of salt. Knead the mixture until a smooth dough forms. Cover the dough with a kitchen towel or plastic wrap and let it rest for 30 minutes.

While the dough is resting, mix the ground beef, ground pork, cooked spinach, breadcrumbs, sautéed onion, one egg, marjoram, nutmeg, salt, and pepper in a large bowl. Stir until all ingredients are well combined.

After the dough has rested, roll it out on a floured surface until it is thin. Cut the dough into squares, about 3x3 inches. Place a spoonful of filling in the center of each square, then fold the dough over to create a pocket. Press the edges firmly to seal.

Bring a large pot of salted water to a boil. Gently add the Maultaschen to the boiling water. Cook for 8-10 minutes until they float to the surface. Remove them with a slotted spoon.

Serve Maultaschen directly in a warm broth or pan-fry them in a little olive oil for a crispier texture.