Mussels are really easy to cook and totally safe once you follow these tips:
1. Empty mussels into your sink and rinse them in cold water. The shells should be tightly closed once they feel the cold.
2. Discard any that are open.
3. To cook, place the fully closed mussels in a saucepan then add about 1 cup of water. Cover the pot with a lid, turn the heat on and bring to the boil, then turn to a simmer.
4. After about 7 minutes, remove from the heat. Check all the mussels and discard any that haven't opened in the cooking process.
5. Remove mussels from the shells and add to chowder.