Chop vegetables (and roughly mince onion into small pieces) and set aside.
Slice chicken thighs into bite-sized pieces and add to a large wok or skillet pan with butter, minced garlic, minced ginger, white pepper, salt, black pepper, and 2 tbsp soy sauce.
Cook on high heat until all chicken is cooked through with browned edges and most liquid has evaporated, about 10-15 minutes.
Remove chicken and set aside.
Add vegetables to the still-hot wok or skillet along with remaining 2 tbsp soy sauce (to “deglaze” any fond on the pan left from the chicken). Cook until onions have softened significantly and the other vegetables have become brighter in color, about 10 minutes.
Serve with your choice of rice and garnish with sesame seeds as desired.