Clean mushrooms and remove stems. Combine olive oil (or butter, melted), lemon juice, and spices until blended. Start fire and when coals are ready, place mushrooms, stem-side down, over direct heat. Brush with oil mixture and cook 2 minutes. Turn and brush heavily with oil mixture and continue cooking additional 2 minutes or until juices are released. Place one tablespoon of goat cheese in center of each mushroom and leave on coals just until cheese softens. Serve on buns with lettuce, tomato and condiments. 6 servings.