In a food processor bowl with metal blade, combine dried mushrooms, salt and black pepper. Cover; process mushrooms to a powder. Add oil, Worcestershire sauce, shallots and garlic. Cover; process mixture till pureed. Stir in thyme and 2 tablespoons rosemary. Using your fingers, gently press the porcini-herb mixture onto all meaty sides of lamb. Cover; refrigerate for several hours or overnight.