I smoke the pork butt in advance, then in the morning I shred the meat into the pot, add minced onions, jalapenos and enough beef broth to keep it moist. Salt to taste. Let it simmer on low all afternoon...
then set out the toppings... refried beans, fresh pico, chipotle slaw, sour cream, guacamole, shredded cheese, fresh limes, salsa, black olives, lettuce... and anything else you can think of. :)
Everyone builds their own.
I topped mine with refried beans and the pulled pork...
then a bit of everything else. They were sooo good! :)