Preheat the oven to moderately hot 200°C (400°F/Gas 6). Lightly grease a shallow earthenware dish.

Peel the onions, place in a large saucepan or stockpot of boiling water and simmer for 5-6 minutes. Remove the onions and drain well. Cool slightly and, using a small sharp knife, hollow out the centres, leaving a 1 cm (1 1/2 inch) rim. Reserve 1/2 cup of onion centres. Season the onions.

Meanwhile, cook the baking in a small frying pan over medium heat until the fay has melted. Chop the reserved onion and add to the pan with the garlic. Cook for 5 minutes, or until lightly golden. Remove from heat, add the cream, egg, nutmeg, parsley and 1/2 cup (40 g/1 1/4 oz) of crumbs. Season well and mix.

Spoon about 1-1 1/2 tablespoons of the filling into the onion shells, piling a little to the top. Combine the remaining breadcrumbs with the parmesan, sprinkle over the onions and dot with butter. Place in baking dish, and carfully pour stock around the onions. Bake, basting occasionally, for 1 hour, or until the onions are tender.