Just before cooking ~.
Give the mussels a good scrub and rinse to remove any excess grit, make sure that they have already had their beards trimmed (if not then trim the beards with a pair of sharp scissors.) The mussels should be firmly closed. If any are open, give them a tap and see if they close. If they do not close, discard them.
Using a large pot, melt the butter over a low heat. Add the shallots, garlic, chilie, and salt (optional.) Cook gently until the onions, garlic and chilie are softened. This could take up to 5 minutes or more. Be careful to watch closely at this stage making sure the butter or the onions do not start to brown. They must be translucent.
Add the wine and zest and increase the heat. Boil until reduced by half. Doing this makes a rich broth. Add the mussels and season lightly with pepper. Stir and then cover the pot with a lid.
After 2 minutes check the dish. Remove the mussels that have opened and transfer to serving bowl. Keep cooking the mussels in the pot still at a boil, removing them as they open. If there are any mussels that will not open discard them.
Pour the broth over the bowl of mussels, sprinkle the dish with chopped parsley.
Serve mussels in separate bowls with a good serving of broth, a wedge of lemon and a slice of thick crusty bread.
When you get the mussels home, remove them from any plastic and place the mussels in a bowl (this helps them to breathe.) Cover them with a clean, damp tea towel or cloth and refrigerate. Kept this way they should keep for two days.