Begin by slicing beef sirloin or flank steak thinly against the grain into strips, ensuring they are about half an inch wide.

In a mixing bowl, combine cornstarch, all-purpose flour, baking powder, salt, and pepper. Whisk together until mixed, then add an egg and gradually incorporate water until you achieve a smooth batter similar to pancake consistency.

Heat a generous amount of vegetable oil in a large frying pan over medium-high heat. Dip each beef strip into the batter, then fry in small batches for 3-4 minutes until golden and crispy.

In a wok, heat a drizzle of sesame oil over medium heat, then add minced garlic, minced ginger, sliced onion, and bell pepper. Sauté for about 2 minutes until fragrant.

Stir in soy sauce, rice vinegar, hoisin sauce, chili sauce, and sugar into the vegetable mixture. Allow the sauce to simmer for around 2 minutes.

Add the crispy beef strips back into the wok, tossing them in the sauce to ensure they’re well coated. Stir-fry everything together for an additional 2-3 minutes.

Garnish with sliced red chilies and chopped green onions before serving with jasmine rice or noodles.