1. Combine beef, breadcrumbs, onion, egg, salt, pepper and thyme; shape into 1 1/2 inch meatballs.
2. In a large flameproof casserole or dutch oven, heat butter and oil; brown meatballs lightly on all sides.
3. Drain excess fat and add remaining ingredients except parlsey, flour and water.
4. (Recipe may be made ahead to this point and refrigerated).
5. Cover and bake at 400 degrees for about 45 minutes or until vegetables are tender.
6. Taste and adjust seasoning.
7. During last 15 minutes of baking, thicken sauce with 2 tbsp flour into 1/2 cup cold water.
8. Add parsley and serve.
9. Note; This casserole freezes well, baked.
10. Thaw completely and reheat at 350 degrees for 30 minutes.
11. You can also freeze in tubs and pop into a crockpot to reheat.