Melt 4 tablespoons of butter in a pan over medium heat.
Thoroughly season your shanks with salt and pepper to taste.
Brown your shanks and onions in the butter (Should take around 2-3 minutes per side). Remove the shanks from the pan and set aside.
Add 2 more tablespoons of butter and continue to brown your onions for around 5 more minutes or until browned and soft.
Pour the pan into the crockpot and add your meat.
Add the rest of the ingredients into the crockpot and then cook on low for 8-10 hours.
After 8 hours, or when meat becomes tender, remove the shank bones.
Shred the meat.
Separate meat and au jus sauce (the juice from the cooked meat). Save the sauce to dip in.
Assemble your sandwiches as you wish. I added the meat and provolone to the hoagie roll and put it in the oven on broil to melt the cheese and toast the bun, but you do not have to.
Dip your sandwich in the au jus and ENJOY!!!