Scrub mussels with a stiff brush, discard any that are open and stay that way even when you close the shell

Discard any with broken shells

Soak them in cool clean water for at least an hour

Mussels are alive and breathing and have taken in sand over time

This allows them to expel the sand

Mussels have a small fibrous "beard" that should be removed

Pull it out toward the hinge of the shell to keep from injuring the mussel

Heat the olive oil in a large pot over medium-high heat

Add the shallots and garlic and cook until soft, about 5 minutes

Add the mussels, wine, buttermilk, butter, and parsley and season well with the kosher salt

Give it a good stir, cover the pot, and cook until mussels open and are cooked through, 10 to 15 minutes

Divide the mussels and the juices between 2 bowls and serve with a crusty whole-grain bread to sop up that wonderful sauce