1. Wash the dried peas in cold running water and place them in a 2- to 3-quart saucepan. Cover with 5 cups of cold water and bring to a boil over high heat. Boil briskly for 2 or 3 minutes, then turn off the heat and let the peas soak in the water for an hour.
2. Skim off any pea husks that may have risen to the surface, add the finely chopped onion, the whole onion, salt pork, marjoram and thyme and again bring to a boil.
3. Immediately lower the heat and simmer with the pot partially covered for about 1¼ hours, or until the peas are quite tender but have not all fallen apart. Remove the whole onion and the salt pork from the soup and cut the pork in slices about ¼ inch thick.
4. "Arter med Flask" may be served in either of two variations. Place a few slices of pork in individual serving bowls. Season the hot soup with salt to taste, and ladle it over the pork.
5. Or, if you prefer, serve the soup alone, accompanied by a separate plate of the sliced salt pork and spicy brown mustard.
NOTE: If domestic yellow split peas are used, they need not be soaked for an hour. Wash them carefully, cover them with 4 cups of cold water and proceed with the recipe as above. They will take somewhat less time to cook than the Swedish peas.
