Rinse the mushrooms, add water, bring to a boil, salt and cook over low heat for 25-30 minutes. Remove the mushrooms with a slotted spoon, let cool and cut into strips. Peel the onion and carrot, cut the onion into cubes. Grate carrots and cheese on a coarse grater. Heat up the oil in a frying pan. Fry the onion, mushrooms and ham for 5 minutes until golden brown on the ham. Then add carrots, mix well, cook for another 5 minutes. Cook cannelloni in boiling water for 10 minutes, season with salt. Throw in a colander, let the water drain. Stuff the pasta with mushrooms fried with onions, carrots and ham. Put the stuffed cannelloni in a baking dish, top with the remaining minced meat, sprinkle with grated cheese. Preheat oven to 180ºC and bake pasta for 4-5 minutes until cheese is melted.