Slice the beef thinly: Freeze the beef for 20–30 minutes to firm it up. Slice into thin strips against the grain so it cooks fast and stays tender.
Marinate briefly: In a bowl, mix soy sauce, vinegar, sesame oil, and egg white.
Toss in the beef and let it sit 10–15 minutes while you prep the sauce.
Make the sauce: In a small bowl, whisk honey, soy sauce, vinegar, ketchup or chili garlic sauce, chili paste, water, and 1 tsp cornstarch. Set aside.
Coat the beef: In a shallow bowl, mix cornstarch with salt and pepper. Lift the beef from the marinade, letting excess drip off.
Toss in cornstarch until each strip is well coated and dry to the touch.
Heat the oil: Pour 1–1.5 inches of oil into a deep skillet or wok. Heat to about 350–365°F (175–185°C). A small piece of bread should sizzle and brown in about 30 seconds.
Fry in batches: Add beef strips in a single layer.
Don’t crowd the pan. Fry 2–3 minutes until golden and crisp; flip as needed. Remove to a wire rack or paper towels.
Repeat with remaining beef.
Optional second fry: For maximum crunch, give the beef a quick second fry, 30–45 seconds per batch. Drain again.
Stir-fry aromatics: Pour out most of the oil, leaving about 1 tablespoon. Over medium heat, sauté garlic, ginger, and sliced red chili for 30 seconds until fragrant.
Add bell pepper if using; cook 1–2 minutes, still crisp.
Glaze with sauce: Give the sauce a stir and pour it into the pan. Cook, stirring, until it thickens and turns glossy, about 1–2 minutes.
Toss the beef: Add the crispy beef to the pan and toss quickly to coat. Work fast so the beef stays crunchy and the sauce clings.
Finish and serve: Turn off the heat.
Sprinkle with green onions and sesame seeds. Serve immediately with steamed rice or noodles, and a side of crisp veggies.