Melt Crisco over medium heat and lightly salt bottom of skillet.
Break ground beef up in skillet and start crumbling into small crumbles.
Add chopped onion while browning meat.
Keep working to break up meat.
When meat is browned, drain off any fat and return to skillet.
Add mustard, vinegar, sugar, and just enough water to barely cover meat in the pan.
Cook, at a simmer, till water is all cooked out-between 15-20 minutes.
Adjust salt and pepper to taste.
Steam buns and serve with a bit of mustard and pickles (can add cheese)