Begin by marinating the sliced flank steak for about 5 minutes. In a bowl, combine the beef with 1 tablespoon of low-sodium soy sauce and 1 teaspoon of cornstarch, ensuring an even coating. Meanwhile, whisk together the remaining soy sauce, rice vinegar, sesame oil, water, hoisin sauce, and sriracha in another bowl; set this flavorful sauce aside for later.

Heat a skillet or wok over high heat, allowing it to warm for about 1-2 minutes. Once hot, spray the pan lightly with cooking spray to prevent sticking. Add the minced garlic and grated ginger, stirring quickly for 30 seconds until fragrant and golden.

Add the marinated beef to the hot skillet and cook for 2-3 minutes, stirring continuously. Look for the beef to turn a rich brown color and become tender. Once it’s nicely browned, remove the beef from the skillet and set it aside.

In the same skillet, add the chopped bok choy stems and sliced red bell pepper, stirring for around 2 minutes. Next, add the bok choy leaves, cooking for another 1-2 minutes until they wilt beautifully.

Return the cooked beef to the skillet with the vegetables. Pour the prepared sauce over the mixture, stirring to combine thoroughly. Allow it to simmer for 1-2 minutes, watching for the sauce to thicken slightly.

Garnish your delicious Bok Choy Stir-Fried Beef with a sprinkling of green onions and sesame seeds. Serve over cauliflower rice or brown rice.