Divide meat into 6 equal-sized patties. Salt and pepper each side liberally.
Melt 2 tablespoons of butter in the skillet. Add the onion and mushrooms and cook over medium heat until browned. Remove from the pan and set aside
Melt 2 additional tablespoons of butter in the skillet and sear the beef patties 3 minutes on each side or until beef reaches 120°F. Remove from the skillet.
Add the last 2 tablespoons of butter to the skillet. Add 1½ cups beef broth. Bring to a simmer and whisk in the flour. Cook until thickened. If the gravy gets too thick, add the remaining 1/2 cup of broth.
Add beef patties, mushrooms and onions back to the hot gravy. Salt and pepper to taste. Cook until desired doneness.
Serve and garnish with sliced scallions.

Divide meat into 6 equal-sized patties. Salt and pepper each side liberally.
Melt 2 tablespoons of butter in the skillet. Add the onion and mushrooms and cook over medium heat until browned. Remove from the pan and set aside
Melt 2 additional tablespoons of butter in the skillet and sear the beef patties 3 minutes on each side or until beef reaches 120°F. Remove from the skillet.
Add the last 2 tablespoons of butter to the skillet. Add 1½ cups beef broth. Bring to a simmer and whisk in the flour. Cook until thickened. If the gravy gets too thick, add the remaining 1/2 cup of broth.
Add beef patties, mushrooms and onions back to the hot gravy. Salt and pepper to taste. Cook until desired doneness.
Serve and garnish with sliced scallions.