Makes: 4 servings. Prep: 30 minutes. Marinate: 1 hour. grill: 6 to 8 minutes.
In a medium-size saucepan, heat oil over medium heat. Saute garlic, ginger and scallions for 2 minutes, stirring often. Add ginger ale, soy sauce, vinegar and hoisin sauce. Gradually bring to a boil over medium-high heat. Once bubbly, reduce heat to medium and cook 10 minutes. Stir cornstarch mixture into sauce. Cook 1 to 2 minutes until thickened. Push through a strainer into a bowl; cool to room temperature. If making ahead, cover; refrigerate until ready to use (bring to room temperature before serving).
Place steak on clean work surface; trim away excess fat. Season both sides with salt and pepper. Heat gas grill to medium-high or prepare charcoal grill with medium-hot coals. Remove 1/2 cup sauce and reserve.
Grill steak for 3 minutes, turn and brush with some of the reserved sauce. Cook 3 minutes, turn again, brush with more sauce. Continue turning and brushing with sauce for a total of 10 minutes or until an instant-read thermometer inserted in the thickest part registers 135°F. Slice and serve with remaining sauce on the side.