Coat the slowcooker with butter. Put the pork, capsicum, teriyaki sauce, rice vinegar, chilli flakes and garlic in the cooker. Cover and cook on LOW until the pork is fork tender, 8-9 hours.
Remove the pork from the cooker and coarsley chop. Add the peanut butter to the liquid in the cooker; stir well to dissolve to make the sauce,
Serve in shallow bowls on the hot jasmine rice and sprinkle each serving with the onions and peanuts.