1. Wash and shred the lettuce.
2. Prepare and slice the onion and potatoes.
3. Skin and crush the garlic.
4. Heatthe stock to boiling point and pour it over the lettuce.
5. Melt the butter in a deep saucepan. Add the onion, potato, and garlic, and fry them gently for 10 minutes.
6. Add the lettuce and stock, bouquet garni, and seasoning to taste.
7. Heat to boiling point; then simmer gently for 2 minutes until the lettuce is tender.
8. Remove the bouquet garni.
9. Rub the soup through a sieve. Add the milk. Re-heat, and add extra seasoning and sugar to taste.