From: Chef Alex Guarnaschelli, Butter, NYC. Yield: 12-18 servings, or 2-3 servings for a table to share.
4½ lb. fresh mussels, thoroughly scrubbed and debearded
3 cups dry vermouth
12 Tbsp. lightly salted butter
1½ lb. white button mushrooms, ends trimmed, quickly washed and thoroughly dried
12 oz. cremini mushrooms, ends trimme