Asian Beef Lettuce Wraps

Name: Asian Beef Lettuce Wraps
Ingredients: 1 1/2 pounds flank steak; Coarse salt and ground pepper; 1 package (3 3/4 ounces) cellophane or bean-thread noodles; 2 tablespoons vegetable oil; 6 scallions, 3 sliced and 3 cut into thirds; 1/4 cup fresh lime juice; 1/4 cup chopped fresh, cilantro; 1 garlic clove, minced; 8 leaves Boston lettuce; 1 ripe mango, peeled, pitted, and cut into strips