Lightly grill the pork belly or shoulder in a pan until the surface is golden brown. Do not fully cook it as it will be simmered later.

Prepare the vegetables by slicing the onion, green onion, and garlic. Set aside.

Mix the sauce ingredients: 1 cup water, 5 tbsp soy sauce, 2 tbsp mirin, 2 tbsp sugar, and a pinch of ginger powder. Add the sliced onion, garlic, and green onion to the sauce and bring it to a gentle boil.

Add the partially grilled pork to the simmering sauce. Cook on low heat until the pork is fully cooked and tender.

Remove the pork from the sauce and slice it into bite-sized pieces. Place the slices on top of a bowl of cooked rice.