Super-Simple, Super-Spicy Mongolian Beef

Whisk together soy sauce, hoisin sauce, sesame oil, sugar, garlic, and red pepper flakes in a bowl.

Toss beef with marinade, cover, and refrigerate 1 hour to overnight.

Heat peanut oil in a wok or large, nonstick skillet over high heat.

Add the green onions, and cook for 5 to 10 seconds before stirring in the beef.

Cook and stir until the beef is no longer pink and is beginning to brown, about 5 minutes.