Brown mince in a pan. Add onions and cook gently until soft. Stir in parsley and tomatoes. Season lightly with salt and pepper. Simmer for 5 minutes.
While mince is cooking, make cheese sauce. Heat oil in a small saucepan. Stir in flour. Cook gently for a minute. Gradually add milk while whisking continuously for a lump-free sauce. Stir in grated cheese.
Grease a 1 1/2 litre ovenproof dish. Place a layer of sliced potato in the bottom. Spoon a little meat sauce over potato, then top with another layer of potato. Continue layering in this manner until mixture is used. Finish with a layer of potato.
Pour cheese sauce over potato dish and gently shake dish so sauce works its way through. Top with extra cheese. Bake for 1 1/2 hours or until potatoes are cooked. Serve with seasonal vegetables.