Ginger Sriracha Sauce:
In a small bowl, whisk cornstarch, ginger, soy sauce, sugar, and sriracha. Set aside.
Beef:
Make the marinade by whisking cornstarch, mirin, ginger, garlic, sesame oil, soy sauce, vinegar, and sugar together in a large bowl.
Add beef to the cornstarch-mirin mixture and toss. Set aside to marinate at room temperature for 20 minutes. Or cover and refrigerate for at least 4 hours or overnight.
Heat a wok or large sauté pan over very high heat. Strain meat from marinade.
Add peanut oil to the wok or pan and stir fry meat, in small batches, for 1 to 2 minutes, until just browned on the outside. Don’t overcook, meat will continue to cook while resting. Transfer meat from wok or pan and place on a plate.
Add ginger-sriracha sauce and scallions and add all the meat back to the pan. Stir to coat. Transfer to a shallow pan or platter and garnish with sesame seeds. Serve with Quick Shiitake Lo Mein, and Chinese Long Beans.