It’s made with dried whole yellow peas, water, salt, onion and a ham hock. Dried herbs can be added as well. All the ingredients are simmered together for about an hour. The ham hock is then removed from the pot, the meat cleaned off it and added back into the soup. The soup is reheated for a few minutes, then served. The soup is usually served with mustard at the table. You can put a dollop of mustard on the rim of the soup plate, or stir a bit of mustard into your soup bowl. Some variations have additional herbs and vegetables such as swede (the root vegetable, not a person) or potato being added.
A more recent version of Yellow Pea Soup is made in Quebec, called “soupe aux pois.” The recipes are essentially the same as the Swedish pea soup ones, though Quebec versions tend to use split rather than whole yellow peas.