Massage pork with sake and soy sauce in a bowl and let sit for 5 minutes.

Cut bell peppers into bite-sized pieces, slice onion into wedges, mince green onion and ginger.

Shape pork into balls and coat with cornstarch.

Heat salad oil in a pan, fry pork balls over medium heat until browned. Add bell peppers and onion, stir-fry until onion turns translucent.

Wipe excess oil, add green onion, ginger, and chili. Stir briefly, then add remaining sauce ingredients and bring to a boil.