Peel onion and garlic. Chop the onion finely, press the garlic through a garlic press. Clean the shiitake and cut into pieces. Cook the noodles in plenty of boiling salted water for ten to twelve minutes.
Heat the fat in a frying pan and fry the mushrooms thoroughly while turning them. Season with salt and pepper and remove. Add onion and garlic to the hot frying fat and fry until transparent. Add stock and cream, bring to the boil and simmer for two to three minutes.
Wash the sage, dab dry and, except for a few leaves for sprinkling, cut into fine strips. Stir the cheese into the sauce and let it melt in the mushroom sauce at low heat. Add the sauce thickener and bring to the boil while stirring.
Season to taste with salt, pepper and lemon juice. Drain the pasta on a sieve and mix with the mushrooms. Halve the ham slices and arrange them on a plate with the noodles. Pour sauce over them and sprinkle with remaining sage leaves.