While the grill is preheating, mix one envelope of au jus gravy mix per package instructions. Add one tablespoon of optional beef tallow. Bring to a boil, then let simmer in order to reduce slightly.
Grate the frozen butter on a box or flat cheese grater.
Use your hands to mix together the ground chuck, remaining packet of au jus gravy mix, ranch dressing mix, and grated butter.
Divide the mixture into four equal parts, and form four patties 3/4" thick. Add a pinch of optional kosher salt to the patties.
Place the burgers on the grill over direct heat. Cook each side for 3-4 minutes until they reach desired doneness as indicated by a reliable quick-read thermometer.
Top with optional cheese, move to indirect heat and close the grills lid. Allow 2-3 minutes for the cheese to melt.
Remove from the grill, and place the patties on the buns. Top with pepperoncini peppers and optional crispy onions, serve with hot au jus gravy for dipping.