Heat up a pan on medium heat, and add neutral oil.
2 tbsp neutral oil
Once the oil is warm, add the diced shallots. Cook until softened but not overly browned, or about 2-3 minutes.
Add the water, light soy sauce, dark soy sauce, oyster sauce, hoisin, sugar, and chicken bouillon powder.
2/3 cup water, 1/2 tbsp light soy sauce, 1 tsp dark soy sauce, 1/2 tbsp oyster sauce, 1/2 tbsp hoisin, 2 tbsp sugar, 1/2 tsp chicken bouillon powder
In a separate bowl, mix the cornstarch and room temp or cold water until the cornstarch is fully dissolved.
2 tbsp cornstarch, 2 tbsp water
Make sure the sauce is at least simmering, then add the cornstarch slurry to thicken the sauce. Stir immediately to incorporate.
Once the sauce has thickened, add the diced char siu and sesame oil. Mix well.
1/4 tsp sesame oil