For the filling, peel and finely dice the onions and garlic. Heat 1 tablespoon of oil. Fry half onions and half garlic. Add frozen spinach, deglaze with 1⁄8 l water, heat for 8-10 minutes. Season with salt, pepper and nutmeg. Pour the spinach into a sieve, squeeze out a little. Dice 1 mozzarella ball very finely. Grate parmesan.
For the rolls, wash the fillets and dab them dry. Cut in half horizontally and tap flat between two layers of foil. Season slices of meat with salt and pepper. Mix spinach, mozzarella cubes and parmesan. Distribute on the slices. Roll them up and fix them with wooden skewers.
For the sauce, heat 1 tablespoon of oil. Fry the rest of the onions and garlic. Sweat tomato paste briefly. Deglaze with tomatoes. Season with salt, pepper, paprika and 1 pinch of sugar and simmer for 6-8 minutes.
Beat the eggs. Mix breadcrumbs with 1 teaspoon salt and 1⁄2 teaspoon pepper. Turn roulades first in egg, then in breadcrumbs. Heat 3-4 tbsp. oil, fry the roulades. Pour the sauce into an ovenproof dish and place the roulades on top. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer) for approx. 35 minutes.
Cut the remaining mozzarella into 6 slices. Place on the roulades approx. 5 minutes before the end of the baking time and bake until done. Serve the roulades with pesto. Roast potatoes taste good with it.
TIP: Homemade bear's garlic pesto (preparation time approx. 10 min.) 150 g bear's garlic wash and shake dry. Remove stalks. Grate 50 g Parmesan cheese. Finely puree the wild garlic, 30 g pine nuts and Parmesan cheese, while letting 75 ml olive oil run in. Season with salt and pepper.