Prepare the Beef: In a large bowl, combine the cornstarch, flour, baking powder, salt, and white pepper. Add the beaten egg and 2 tablespoons of vegetable oil, mixing until a smooth batter forms. Add the sliced beef strips to the batter, ensuring each piece is well coated.

First Fry: Heat vegetable oil in a deep fryer or large pot to 325°F (160°C). Carefully add the beef strips in batches, ensuring not to overcrowd the fryer. Fry for 2-3 minutes, until lightly golden. Remove the beef and place it on a wire rack to drain.

Second Fry: Increase the oil temperature to 375°F (190°C). Fry the beef again for 1-2 minutes, until deeply golden brown and crispy. Remove the beef and place it back on the wire rack to drain. The wire rack is crucial; it prevents the beef from steaming and becoming soggy.

Make the Sauce: While the beef is frying, prepare the sauce. In a wok or large skillet, heat 2 tablespoons of vegetable oil over medium heat. Add the minced garlic, ginger, and chili, and stir-fry for 30 seconds, until fragrant.

Combine: Pour in the rice vinegar, soy sauce, ketchup, brown sugar, honey, sesame oil, and chili flakes (if using). Bring the sauce to a simmer and cook for 2-3 minutes, until it thickens slightly.

Coat the Beef: Add the crispy beef to the sauce and toss to coat evenly. Ensure every piece is covered in the glossy, flavorful sauce.

Serve: Transfer the Crispy Chilli Beef to a serving plate. Garnish with sesame seeds and chopped spring onions. Serve immediately.