Melt your butter in a skillet on your stovetop over medium-high heat
Add in as much of your chicken as will fit in your pan, cooking a few minutes on each side until it is golden, repeat for remaining chicken
Place your onions in the bottom of your crock pot
Put your browned chicken on top of your onions
In a separate bowl, mix together your ketchup, cider vinegar, molasses, Dijon mustard, onion powder, ground cumin, garlic powder and hot sauce
Pour your sauce all over your chicken
Cover and cook on low for 4 hours (your chicken will be tender and the sauce thick when it is done)
Shred your chicken with forks (or a mixer, whichever you prefer) and serve on buns