Mix eggs, buttermilk 1/8 litre water and flour to a smooth pancake batter. Cover and let it swell for about 30 minutes. In the meantime, segregate the spinach, wash thoroughly and drain.
Peel and chop the onions and garlic. Heat 20 g fat in a pot, fry garlic and half the onions in it. Add the spinach and fry covered for 4-5 minutes. Season with salt, pepper and nutmeg and let it cool down a bit.
For the tomato sauce, heat oil in a pot and sauté the rest of the onions in it. Add the tomatoes and juice. Bring to the boil, stir in broth and chop the tomatoes. Add Italian herbs, season with salt and pepper and simmer at medium heat for about 10 minutes.
Heat 10 g fat in a large, coated pan (24-26 cm Ø) and pour 1/4 of the pancake batter into the pan. Bake the pancakes on both sides until golden brown. Bake 3 more pancakes from the remaining batter in the remaining fat.
Cut mozzarella into thin slices. Cover pancakes with spinach and mozzarella and roll them up. Put tomato sauce in an ovenproof dish. Cut the pancakes diagonally into thick slices and spread in the dish.
Sprinkle pine nuts over it. Gratinate in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 25 minutes.