Heat 3 tablespoons of the butter in a frying pan over medium heat and saute onions about 5 minutes.
Add boiling water and simmer, uncovered, for 20 minutes or until most of the liquid has cooked away.
Meanwhile, combine the ground beef, salt, pepper, garlic salt, and smoke-flavored salt; mix until blended, then shape into one 8-inch patty.
Melt the remaining 1 tablespoon butter in an 8-inch cake pan.
Fit the meat patty into the pan.
Cook on top of range over medium heat for about 5 minutes or until nicely browned on bottom.
Set into a preheated broiler about 3 inches below heat and broil about 6 minutes for meat cooked rare, a few minutes longer for medium-well done.
With a slotted spatula transfer meat to a rimmed platter.
Add sour cream to onion mixture; stir over medium heat just until heated—do not boil.
Pour sau,ce over meat and cut in wedges to serve.
Garnish with sprigs of parsley