Mussels are commonly sold in two-pound bags in the US (often mesh bags, which allow them to breathe). "Check the attached tag to see the harvest and ship date," advises EricMM. "It should have been within the previous week. Most will be open a crack ... that's OK. Sniff the bag—this is the most important step of all in purchasing mussels! There should only be a faint briny smell. Anything stronger, do not buy!"
When you place the mussels in cold water, they should start to close, EricMM says. If one doesn't close, set it aside; if it hasn't closed in five minutes, it is dead and should be thrown away. Farmed mussels often don't have beards, but removing mussels' beards and cleaning them is straightforward; here are illustrated instructions.
Mussels cook quickly, notes hotoynoodle: "As soon as they open they're finished." If any don't open during cooking, discard them. EricMM thinks the most flavor can be extracted from mussels by putting them in a dry pan, covering it, and letting them steam in their own juices.
Many like them steamed in white wine, butter, and garlic. Harters also likes them cooked in tomato sauce with garlic and onion. "Simple is best," he says. bushwickgirl makes a rich dish by cooking them with shallots, heavy cream with a bit of saffron bloomed in it, and a shot of Pernod, with basil chiffonade for garnish. She also likes steamed mussels in lemongrass-coconut curry.
Discuss: cooking mussels?