Pour your mussels into a sieve and leave SAP away if necessary. Let your sink full of cold water, put mussels in it, check for broken shells or mussels that no longer close after rinsing. Throw it away.
Peel and cut the onion into fine rings, finely chop the celery. Add a lump of butter in one large pot or 2 smaller pots with lid, which works the easiest because you have to shake, divide onion and celery and let it bake, sieve the mussels and add, season with salt and pepper, put lid on it. After 2 minutes you shake up and cook for 1 minutes at high temperature. Check if the mussels are open and turn off the heat.
Fry the fries. Fry the salicornia short and powerfully in butter with some pepper. Put everything on the table and serve in a deep plate, choose your favorite toppings.
Tips
Test all your toppings, you will be amazed how many different flavors the mussel can get, and ambiance insured at the table! Do you have mussels left? Then remove them from the shell and save in the gravy. You can also impose them in vinegar or make mussel soup out of it!