Hamburger steak smothered in brown gravy with mushrooms and onions

Ingredients
2 lbs Ground Chuck
1 Yellow Onion thinly sliced
16 oz mushrooms I used a blend of cremini and shitaki
2 cups beef broth – divided. I use canned fat-free low sodium
2 tbsp all-purpose flour
6 tbsp butter
4 sliced scallions white and green sections
salt and pepper to taste
.
Instructions
Divide meat into 6 equal-sized patties. Salt and pepper each side liberally.
Melt 2 tablespoons of butter in the …