Celery Soup II

3 stalks celery

3 cups milk

1 slice onion

3 tablespoons butter

3 tablespoons flour

Salt and pepper

1 cup cream

Break celery in one-inch pieces, and pound in a mortar. Cook in double boiler with onion and milk twenty minutes. Thicken with butter and flour cooked together. Season with salt and pepper, add cream, strain into tureen, and serve at once.