Wipe the pan with a kitchen towel, and add the last 2 tablespoons of oil. Over medium heat, sauté onions and garlic until soft, about 6-7 minutes.Transfer to the casserole dish. Add the stock, water, diced tomatoes, paprika, salt, pepper and basil to casserole dish. Bring to a boil, then reduce to simmer and cover and cook 1 ½ hours. Add carrots and sweet potatoes, cover and cook for another 25-30 minutes, or until tender. Stir in frozen peas, cover and simmer for another 5 minutes before serving.