1 lb. spaghetti
2 tbsp. olive oil
1 onion, chopped fine
2 c. tomato puree
1/2 tsp. salt
1/4 tsp. pepper
1/2 c. grated Parmesan cheese
1/2 lb. mushrooms, washed & peeled or 1 lg. can mushrooms
1 lb. chicken livers
1/4 lb. butter