Finnish Pea Soup in a Slow Cooker
If you can find some, I highly recommend Turun sinappi or Auran sinappi Finnish mustard.
You can use normal salt if smoked salt is not available.
If cooking without a slow cooker, you should cook on a low temperature for 3 to 5 hours, and remember to stir it often. Also, you should use at least 13 cups of water.