Place drained, dried peas in soup kettle. Add chicken broth; bring to a boil; simmer on low for 10 minutes. Skim froth from top of soup. Melt butter in skillet; saute carrots and onions until onions are golden; add leeks and lettuce; simmer on low for 10 minutes. Stir vegetable mixture into soup; add sugar and salt. Simmer until split peas are tender, about 2 hours. Put fresh peas through a sieve. Force soup mixture through a sieve, also. Return this combined mixture to the kettle. Stir in cream and milk. Heat just to boiling; stirring occassionally to prevent scorching. Just before serving, add butter. Garnish with a dollop of sour cream, a dash of sherry, or both. Elegant! ----