In a large saucepan, place pork, water, soy sauce, slice of ginger, and star anise, and cook, uncovered, over medium heat, for 1 hour.
Remove pork from liquid and cool thorughly; then slice into thin medallions.
Mix together miso, sriracha, sherry, vinegar, and sugar, set aside.
Stir-fry garlic, ginger, and red peppers in wok with oil over high heat for a few seconds, then add onions and pork slices, and cook for about 1 minute.
Add the bell peppers and cook a few minutes more until the peppers are crisp-tender.
Add reserved miso sauce mixture and cook until heated through.