Cover the peas with the cold water in a large saucepan; let stand overnight.
Put smoked shoulder butt into a large saucepot with the 3 quarts water and onion.
Simmer 1 1/2 to 2 hours, or until meat is tender.
Remove meat and set aside.
Skim fat from liquid, leaving about 2 tablespoons.
Drain the peas and add to the broth with the remaining ingredients.
Cook slowly until peas are tender.