Wash, clean and possibly chop the spinach. Peel onion and garlic and chop finely. Heat the oil in a pot. Sauté onion and garlic, add spinach and 100 ml water.
Steam for about 5 minutes with the lid closed. Season with salt, pepper and nutmeg. Drain the spinach in a sieve and put it in a cool place. For the béchamel sauce, melt the fat in a saucepan, add the flour and sauté.
Deglaze with milk and 250 ml water, stir in broth. Bring to the boil, simmer for about 5 minutes. Season with salt and pepper. Grease a suitable casserole dish (approx. 10 x 36 cm). Spread some béchamel sauce thinly on the bottom of the casserole dish.
Place 4 lasagne plates on top. Spread some sauce on the plates. Put half of the spinach on top. Put half of the ricotta cream cheese on the spinach. Spread the ham slices evenly, spread with béchamel sauce and cover with 4 lasagne sheets.
Repeat the whole process (sauce, spinach, ricotta cheese, lasagne sheets). Pour the rest of the sauce onto the last layer of lasagne sheets. Grate the cheese and sprinkle over the lasagne. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 30 minutes until golden brown.