Rinse mussels quickly in 2 changes of cold water. Do NOT leave in water. Trim off barnacles and beards. Discard those that are open and won't close when squeezed.
In a large wok with lid, sauté shallots in butter. Add pressed garlic, salt, pepper and bay leaf. When shallots are translucent, sprinkle on flour. Stir to combine. Add white wine, cream and parsley. Whisk. Cover. You do not want the liquid to evaporate. Cook gently for 5 minutes or so..add another 2-3 tablespoons white wine. Cook again, covered, for 5 minutes or so. Add a small squeeze of lemon juice. Stir. (this can be done 1-2 hours ahead if you want)
Add mussels to hot sauce. Cover and steam just until open, tossing gently once. The sauce is somewhat thick when the mussels are added but the juice from the mussels thins the sauce to the right consistency and obviously adds flavor.
Remove from heat and serve! Discard those that did not open. Don't leave on the heat...they will overcook. Reheat to serve a second round.