1. Heat oil in large pot; add onion and sauté until golden.
2. Add celery and carrots and sauté until soft. Add roast to pot and brown on each side.
3. Mix together wine, ketchup, salt and pepper. Add to the pot.
4. Cover pot and cook over low heat until meat is fork-tender (approximately two hours).
5. Add sliced onions, mushrooms, and cornstarch mixture. Boil until gravy thickens. Allow roast to cool before slicing.