Although they are rarely served in fine restaurants and almost never appear in smorgasbords, soups are essential in traditional Swedish cuisine. One soup in particular, ärtsoppa, has a distinguished history.

Yellow split pea soup has sustained the working class since Viking times. When Catholicism was the reigning religion in Sweden, ärtsoppa, which is peppered with salt pork, became the favorite meal before Saturday each week.

Today, though the Catholic Church has few followers in efficiently secular Sweden, the soup is still eaten every Thursday in many homes. Ärtsoppa is always served with mustard; You either add a little mustard to the soup to season everything, or you dip the tip of your soup spoon into the spicy seasoning before each bite.

Yellow pea soup (Ärtsoppa)

Serves 4 to 6

1 pound whole dried yellow peas (split peas are okay)

2 onions, finely chopped

1 whole onion, peeled, cut in half and each half glued with 1 whole clove

1/2 pound lean salt pork

1/4 teaspoon marjoram

1/2 teaspoon thyme

Salt (if necessary)

whole wheat mustard

1. Soak peas in water for at least 12 hours.

2. Drain the peas, put them in a large saucepan, cover with 6 cups cold water, chopped onion and the onion halves with cloves. Bring to a boil, then reduce heat to medium. Add the salt pork, cover, and simmer for about 90 minutes, skimming any foam that rises to the top. Add the marjoram and thyme to the pan, stir, and simmer another 15 minutes. Season to taste with salt. Remove pork, allow to cool until comfortable to handle, then cut into chunks. Remove and discard the onion halves with your teeth.

3. Divide the pork among rimmed bowls, then ladle the soup. Pass a bowl of grainy brown mustard across the table.

Enjoy this wonderful Swedish tradition served warm with pieces of bread.