Drain the salmon, reserving 3/4 cup of the liquid. Flake the meat. Melt butter in a large skillet over medium- high heat. Add onion, and cook until tender.
In a medium bowl, combine the onions with the reserved salmon liquid, 1/3 of the cracker crumbs, eggs, parsley, mustard and salmon. Mix until well blended, then shape into six patties. Coat patties in remaining cracker crumbs.
Melt shortening in a large skillet over medium heat. Cook patties until browned, then carefully turn and brown on the other side.
