How to Make It
Heat butter in a medium saucepan over medium- high. Add shallot and cook until translucent, about 1 minute. Add mussels and wine; cover and cook until mussels fully open, 3 to 5 minutes (discard any that do not open). Remove from heat and stir in tarragon, salt, and pepper.
Using a slotted spoon, transfer mussels to serving bowls; spoon sauce over top. Serve with crusty toasted bread, if desired.