Defrost the spinach. Cook the lasagne plates al dente. If the plates are not boiled, soak them briefly in water.
Peel and finely chop the onion and garlic and sauté in butter until translucent. Sprinkle in the flour and sweat, then add the milk and the stock while stirring and bring to the boil. Season with salt, pepper and nutmeg and add the diced ham.
Peel, core and dice the tomatoes.
Line the bottom of a greased casserole dish with a third of the pasta, spread a third of the sauce on top and put half of the spinach on top. Cover with half of the tomatoes. Layer everything again in this order, then finish with pasta sheets and pour the remaining sauce over it. Sprinkle with the two types of cheese and bake in the preheated oven at 180 ° top and bottom heat for about 40 minutes.