Clean the mushrooms, wash briefly and cut into thin slices. Peel and finely chop the onions. Heat oil in a pan. Fry the mushrooms in it in 2 portions for about 5 minutes. Add onions and fry for about 2 minutes.
Season with salt and pepper.
Heat butter for the béchamel. Lightly sauté the flour in it. 1⁄4 Stir in l water and milk. Bring to the boil and simmer for about 5 minutes. Stir the herb cream cheese into the sauce. Season to taste with salt, pepper and nutmeg.
Cut the ham into small cubes. Finely grate the parmesan. Cut lasagne sheets in half crosswise. Grease four small casseroles (each approx. 11 x 11 cm; 4 cm high) or one large casserole. Pour 1 tsp. sauce into each dish.
Place half a lasagne plate on top, spread 1⁄3 mushrooms, ham and béchamel on each. Layer the remaining ingredients in the same way. Finish with béchamel and sprinkle with parmesan. In a preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see
manufacturer) Bake for 30-40 minutes.