Mongolian Beef

Name: Mongolian Beef
Prep time: 15 min
Cook time: 10 min
Total time: 25 min
Cuisine: Chinese
Ingredients: ¼ cup oil for cooking (I use avocado oil or any neutral flavor cooking oil with high smoke point would do); 1 lb flank steak (Slice it against the grain into 1/4-inch (6-mm) pieces (Note 1)); ¼ tsp baking soda ((Note2)); 4 tbsp cornstarch (divided); 1 tbsp light soy sauce (or tamari); ¼ tsp ground white pepper; 1 medium yellow onion (sliced); ½ large red bell pepper (thinly sliced); ½ large green bell pepper (thinly sliced); 6 scallion; 1 tbsp garlic (grated); 1½ tsp ginger (grated); 2 tbsp Chinese cooking wine ((Note3)); 2 tbsp hoisin sauce; 3 tbsp light soy sauce (or tamari); ¼ tsp Chinese five spice powder; 1 tsp sesame oil; 1 cup water; 2 tsp cornstarch; ¼-½ tsp chili flakes ((Note4)); sesame seeds (optional)