Rub pork butt with Italian seasoning, red pepper flakes, salt and pepper.
Preheat pan to high heat. In hot pan, sear pork on all sides, 2 to 3 minutes per side
Cut whole head of garlic in half horizontally, and roast in pan while searing pork.
Place pork and garlic in slow-cooker.
Keep pan on heat, add onions and fennel.
Sauté until golden, then add balsamic vinegar, scrap bottom of pan and reduce by half
Add onions, fennel and reduced balsamic to slow-cooker as well as remaining ingredients
Cook 4-5 hours on low setting or until meat is fork-tender.