Beef Leftover - cooking recipe

Ingredients

2 1/2 c. shell macaroni, raw
1/4 c. onion, diced
3 c. roast beef, diced
1/4 c. or less oil
2/3 c. tomato paste
2 c. beef stock
1 tsp. dry mustard
1/2 tsp. salt
1/4 tsp. pepper
2 Tbsp. celery, chopped

Preparation

Fry onion in oil.
Add other ingredients except macaroni. Simmer 3 minutes.
Add macaroni.
Add sauce.
Place in casserole and bake at 350\u00b0 until macaroni is done.
Start testing at 30 minutes or can be covered and cooked on stove top.