While it's true that steaming makes it impossible to burn food, you can still over-cook it (of course, undercooking is possible as well). This means that, when it comes to fish and mussels, cooking time is extremely important. One way to steam seafood is in a classic metal steam basket. Remember - if any of your mussels don't open during steaming, it means they were dead before cooking and should be thrown away. A second way of steaming seafood is to wrap it in wet cooking parchment and pop it in the oven. Just be sure to seal the parchment tightly so the steam can't escape.