Preheat the oven to 180°C.
Peel, dice and cook some root vegetables in boiling water, then drain. Add some butter/margarine and milk and mash it into a textured or smooth purée, according to your liking. Season with salt and pepper, then set aside. You should get about 2 cups of mash.
Thin the gravy with some stock, if it’s too thick. Mix in the garlic.
Cut the onion into thin slices.
Cut the roasted/cooked vegetables into slices or chunks, then line the base of a baking dish with them. Scatter some shredded meat on top, then half of the onion and pour over half of the gravy. Add another layer of veggies, onion and the chopped parsley. Pour over the gravy.
Spoon the mash on top, spreading it evenly. Using a fork, make some marks on the surface.
Bake for 20 minutes, until golden, then scatter some cheese on top and grill for 5 minutes.