Ingredients:

1/2 cup soy sauce
1/2 cup sake
1/4 cup (packed) dark brown sugar
3 tablespoons minced peeled fresh ginger
1 tablespoon balsamic vinegar
4 garlic cloves, crushed
1 2-pound flank steak
1 pound asparagus, trimmed, cut into 1 1/2-inch lengths
3 tablespoons peanut oil
2 red bell peppers, cut into 1-inch-wide strips
1 1/2 pounds crimini mushrooms, halved, each half cut crosswise into 1/4-inch-thick slices
4 green onions, cut into 1-inch lengths
2 teaspoons cornstarch

Method:

Combine first 6 ingredients in 13×9x2-inch glass baking dish. Add meat. Cover and refrigerate at least 2 hours and up to 1 day. Let stand at room temperature 1 hour before continuing.

Cook asparagus in large pot of boiling salted water until crisp-tender, about 4 minutes. Drain. Rinse under cold water to cool. Drain again.

Heat 2 tablespoons peanut oil in heavy large skillet over medium-high heat. Add red bell pepper strips and sauté 3 minutes. Add crimini mushrooms and sauté until mushrooms are soft, about 5 minutes. Add green onions and asparagus and sauté until vegetables are tender, about 2 minutes longer. Transfer vegetables to serving platter. Tent with foil to keep warm.

Heat remaining 1 tablespoon peanut oil in same skillet over high heat. Remove steak from marinade; reserve marinade. Add steak to skillet and cook to desired doneness, about 4 minutes per side for medium-rare. Transfer to cutting board. Tent with foil and let stand 5 minutes.

Meanwhile, place reserved marinade in small saucepan. Whisk in cornstarch. Whisk over high heat until sauce thickens and boils, about 3 minutes. Remove sauce from heat. Season sauce to taste with salt and pepper.

Cut steak across grain on diagonal into 1/2-inch-thick slices. Arrange steak slices atop vegetables on platter. Spoon some of sauce over meat and vegetables. Serve, passing remaining sauce separately.