Heat the oil in a pan. Chop the onion finely and put it to fry. Meanwhile, wash and slice the mushrooms. Add them to the onions, stir and leave to cook gently.
4-5 minutes later, add the minced meat and stir until well distributed and there's no large lumps anymore. Finally, season with spices and add walnuts. In a greased oven dish, arrange several phyllo pastry sheets - more is better.
Put all the stuffing on and cover well with the same number of phyllo pastry sheets. Pour a little oil on top and put to bake until browned.