In a large frypan, brown grated chicken in butter or margarine. Add onions, chilli, garlic, basil and oregano. Then add the spaghetti sauce, tomato puree and salsa. Stir all together. Cover frypan and simmer for 10 minutes over low heat.
In a lightly greased 20x30cm baking dish, place a layer of tortillas, then a layer of the chicken/sauce mixture, then a layer of mozzarella cheese. Repeat layers twice, then top with Cheddar cheese and bake in the preheated oven for about 1 hour, until cheese is bubbly.