Peel the onions leaving them whole. Place in a saucepan, cover with cold water and bring to the boil. Simmer for 10 minutes then drain. Place in a casserole, season with salt and pepper and sprinkle over the sugar. Add the stock. Cover with a lid, place in a moderate oven (180°C., 350°F., Gas Mark 4) and bake for 25–30 minutes or until tender.
Remove the onions from the casserole and pl