Spray a 20cm square baking dish with low fat cooking spray.
Alternately layer the onions, potatoes and garlic beginning with onion and ending with potatoes, sprinkle each layer with flat leaf parsley. Spray with more low fat cooking spray and pour over the vegetable stock.
Cover with foil and bake for 45 minutes. Remove foil and bake for a further 30 minutes. Serve straight from dish or cut into rounds using a cookies cutter.