Heat the oil in a large saucepan and fry the onion and garlic until softened. Add the mince and break it up with the side of a spoon as it cooks. Cook until browned
Stir in the dried herbs and flour. Gradually add the stock and Worcestershire sauce and bring to the boil. Reduce heat and simmer whilst preparing the potato topping.
Heat the oven to 190℃/180℃ fan/gas mark 5. Peel the potatoes and cut into even sized pieces. Place in a pan with enough water to just cover. Bring to the boil, add a pinch of salt and cook for about 10–15 minutes until the potatoes are tender.
Drain well and return to the pan. Add the milk and butter, season to taste and mash well.
Season the meat to taste and spoon off any excess fat. Pour into a shallow ovenproof baking dish. Carefully spread the mashed potato on top of the mince, fluffing the top with a fork. Sprinkle the cheese over the top if using.
Bake for 30 minutes or until the potato is crisp and golden.
Freeze: Freeze after topping with the potato (allow to cool completely first) for up to 4 months. Defrost completely before baking in the oven. Increase the cooking time by 10 –15 minutes. Cooked meat should only be reheated once so do not freeze if using leftover meat.