Mussels are a pretty good bet if you're looking for sustainable seafood, although it's worth avoiding those collected using dredging methods. The MCS have given them a range of ratings from 1-3 depending on collection method, 1 and 2 is the best place to be.
This is so incredibly easy to make, but you can make it a little harder (and much tastier) by pairing it with some Kingshill Bread!
Take both the mussels and the butter out of the fridge to come up to room temperature.
Thickly slice a white onion and smash/crush a couple of garlic cloves. Heat up a deep saucepan with some olive oil and fry the onions and garlic until soft. Add a finely chopped red chilli and slosh in a glass of white wine.
Pick through your mussels (1kg serves 2 people) giving them a sharp tap, or in my case stick a teaspoon through the opening and giving them a gentle nudge, to make absolutely sure they are safe to eat. If they don't close then they aren't safe - don't eat them.
Make sure the wine mixture is bubblingly hot, keep the flame up high, put the mussels into the saucepan quickly and clamp the lid down.
While they are cooking, slice up some bread and apply outrageous amounts of butter.
Keep an eye on the mussels, it should only take about 8 minutes to cook them but what you are looking for is all the shells to be open. Any that don't open should be thrown away as carriers of instant stomach death.
Spoon out the mussels between two bowls, spooning the oniony, winey sauce over the top. Eat with your fingers and don't spare the butter.