Bring a large saucepan of water to the boil. Add chopped potato and sweet potato and cook until tender. Drain the water and return potatoes to the pan. Add margarine and Vitasoy Oatmilk and mash until smooth.
Heat oil in a deep frying pan, add onion, garlic and capsicum, cook until onion becomes translucent. Add beef mince and brown until almost cooked, drain any excess fat from the pan.
Add the bay leaf, chopped tomatoes, tomato paste, crumbled beef stock cube and water, and then simmer for around 10 minutes until the mince is cooked through. Remove from heat and mix through basil.
Place the mince mixture in the base of a casserole dish, top with the potato mash and spread evenly to cover the mince mixture. Sprinkle with oats and bake at 170°C for 30-40 minutes until top is browned and heated through.