Clarifying Consommé with a Raft

Consommé is stock cleared until you can read through it. Mix 500 g lean ground beef, a finely chopped onion, carrot and celery, tomato and four egg whites. Stir that into 2 litres of cold, fat-free stock and heat it slowly, stirring now and then until it reaches 50°C. Then stop stirring. The egg and meat rise and form a raft that traps cloudy bits. Poke a hole in the raft and simmer gently for an hour, basting through the hole. Ladle it out through a cloth-lined sieve without breaking the raft.