Whisk soy sauce, sugar, rice wine vinegar, garlic, and 1 tablespoon sesame seeds in a bowl; pour into a resealable plastic bag. Add beef, coat with marinade, squeeze out excess air, and seal bag. Marinate beef in the refrigerator overnight.
Heat peanut oil in a wok or large skillet over medium-high heat; cook and stir beef and marinade until beef is well-browned, about 5 minutes. Stir in asparagus, mushrooms, onion, bell pepper, and green onions; cook and stir until vegetables begin to soften, 3 to 4 minutes. Add cashews and 1 tablespoon sesame seeds; continue cooking until vegetables are tender, 2 to 3 minutes more.
Mix cornstarch and water in a small bowl; stir into beef stir fry until sauce is thickened, about 3 minutes. Sprinkle with remaining 1 tablespoon sesame seeds.
