Spaghetti Beef Casserole

3 T. Oil
2 lbs lean ground beef
2 med. onions, chopped
2 cans (4 oz each) mushrooms, drained
2 cans (8 oz. each) tomato sauce
1 can (6 oz) tomato paste
1 t. oregano
1 t. garlic powder
2 packages (7 oz each) spaghetti
1 package (8 oz) cream cheese
2 cups cottage cheese
1/2 c. chopped chives
1/2 c. sour cream

Heat oil in skillet.  Add beef and onions; cook until onions are translucent and beef is lightly browned.  Combine mushrooms, tomato sauce, tomato paste, oregano, garlic powder; add to meat.  Mix well and simmer uncovered 15 minutes.  Cook spaghetti as directed on package; drain.  Place half of the cooked spaghetti in buttered baking dish.   Mix cream cheese, cottage cheese, chives and sour cream.  Spoon half onto spaghetti.  Top with half of meat mixture.  Repeat layers.  bake at 350 for 30 minutes.