Boil potatoes until tender then drain them. Add butter and mash until smooth. Add milk and beat to combine.
Heat oil and fry the onion, garlic and vegetables until they are soft. Add minced lamb/beef, sauce and beef stock. Keep on stirring until mixture comes to the boil. Simmer for 3 minutes. Set aside to cool.
Preheat oven to 200oC. Sppon mixture into small ramekin dish if you prefer personnal size or big oven dish if you want to serve them together. Top with mashed potato. Rake the top with a fork then sprinkle the cheese. Bake for 15-20 minutes or until golden.