Scrub and debeard the mussels, discarding any that remain open. Combine the wine, onions, bay leaf, thyme, rosemary and garlic and bring to a simmer. Add mussels, cover the pot and steam until the shells open. Remove the mussels and keep them warm while finishing the sauce. Strain the steaming liquid, whisk in butter, add parsley and chives and season to taste with salt and pepper. Serve the sauce ladled over the mussels.