1. Heat oil in a large, flameproof casserole dish (20-cup capacity) over a medium heat. Add onion, garlic and celery. Cook, stirring occasionally, until onion is soft.
2. Add chicken and bacon. Cook, stirring occasionally, until chicken has changed in colour. Add rice, stock and mushrooms. Season with salt and pepper. Stir to combine. Bring to boil. Cover with lid.
3. Cook in a moderate oven (180C) for 15 minutes. Remove and stir in peas and corn. Return to oven for a further 5 minutes or until rice is tender.4. To serve, stir in cheese and parsley.
Any leftover risotto can be kept in the refrigerator for up to 2 days ahead. To reheat, stir in extra stock or water. Any frozen vegetables can be stirred into risotto. Or boil or steam chopped sweet potato, pumpkin, broccoli or asparagus. Chopped ham, smoked chicken or seafood can be added. Risoni, rice-shaped pasta, can be substituted for the Arborio rice, if you prefer.