Fish Soup

1 lb. cod or halibut
1 quart milk
1 sliced onion
1 table-spoon white roux

Cook the fish in boiling salted water until it flakes easily. Drain it. Take away the bones and skin and rub the fish through a sieve. Put the sliced onion in the milk and boil for ten minutes. Remove the onion. Add the white roux (see [p. 12]) to the milk. Stir till well mixed. Add the fish. Season.