I have been making this "broth" over many years. It is a development from my love of moules Provençal but really is a mussel casserole. Enough for 4 generous portions. To be honest, I make it slightly differently every time I do it and the veg additions vary depending on what is in my larder!
I make this even just for myself and portion up the mussels and add the broth into freezer containers as single portions. Cool in the fridge then freeze in my chest freezer and I use then within a month. I am very much a "cook to taste" cook and with well like recipes like this I do it with whatever I have in house/larder/garden and tasting as I cook is definitely my style of cooking. I grow herbs in my garden and always have fresh parsley /chives/ rosemary, thyme available as well as a well stocked cupboard of dried herbs and spices.
Chop up your home made bread into big chunks and put on the table in a basket. Put a good sized empty bowl on the table for the shells. And I suggest that instead of napkins each diner be given a hand towel. Mussels this way call for fingers with a soup spoon for the broth! And 2 bottles of a good Muscadet (and my 1 year old home made Melon de Bourgogne is always on hand) will make an excellent meal go with relish for 4 diners.