In a small bowl, whisk together soy sauce, honey or sugar, cornstarch, and water. Set aside.

Heat the cooking oil in a large pan or wok over high heat until very hot.

If using, add grated ginger and minced garlic and stir-fry for about 30 seconds until fragrant.

Add the sliced beef to the hot pan and stir-fry quickly until browned on all sides, about 2-3 minutes. Do not overcrowd the pan; cook in batches if necessary.

Add the sliced onion and bell pepper to the pan. Stir-fry for 3-4 minutes until vegetables are slightly softened but still have a bite.

Pour the prepared sauce mixture into the pan. Stir continuously until the sauce thickens and coats the beef and vegetables, about 1-2 minutes.

Remove from heat. If using, stir in chili flakes. Garnish with sliced spring onions and sesame seeds before serving.