1. Separate the lettuce leaves from the head and wash them well.
2. Tear into small pieces.
3. In a heavy bottomed saucepan, combine the shredded lettuce leaves with onions, sugar and stock.
4. Bring to a boil then reduce the flame and cover the pot.
5. Steam for 20 minutes, shaking the pot occasionally to stir contents without removing the lid.
6. Add the shelled peas, butter and seasoning stir well.
7. Recover and simmer for another 25 minutes until tender.
8. Ladle into warm soup bowls and serve piping hot.