Combine beef with chicken bouillon, MSG, salt, white pepper, sugar, oil, baking soda, water, and cornstarch in a bowl. Mix well and marinate for at least 30 minutes.
Dip marinated beef pieces into wet batter, allowing excess to drip off.
Coat battered beef evenly with dry cornstarch for extra crispiness.
Heat oil in a wok or deep frypan over high heat until hot (around 180°C).
Fry beef in batches for 3–4 minutes or until golden brown and crisp. Remove and drain well.
Heat 2 tbsp of oil in a clean wok over medium-high heat.
Add onion, spring onion, garlic, and dried chilies. Stir-fry for about 30 seconds or until fragrant.
Add tomato sauce, CHIN-SU hot sauce, oyster sauce, dark soy sauce, Thai sweet chili sauce, white vinegar, and sugar. Stir until sauce thickens slightly and becomes glossy.
Add fried beef back into the wok. Toss quickly to coat each piece in the sauce.
Serve hot over cooked jasmine rice. Garnish with sliced green onions or sesame seeds.
