Melt butter in a pot deep enough to hold the mussels over medium heat. I used a heavy dutch oven.
Add garlic, shallot, fennel, saffron, lemon zest, salt, and preserved lemon. Cook until the fennel is just starting to soften but still toothsome.
Give it a good stire, add the mussels, toss to coat with the goodies in the pan.
Pour in the beer beer, and bring to boil with the lid on.
Reduce to simmer. Cook 4-5 min until mussels are just open. You don’t want to overcook them! No one likes a leather mussel. Discard any unopened.
Top with parsley, fennel frond, and celery leaf, and serve with toasted or grilled bread & a glass of saison.