(adapted from Cooking Light)
1 pound ground beef
1-2 tablespoons flour
1/2 cup thinly sliced onion
freshly ground black pepper
1 cup sliced cremini mushrooms
1 1/2 teaspoons flour
1/4 cup dark beer (or beef broth, if you prefer)
8 sliced rye bread
4 slices provolone cheese
Preheat oven to 400F.
Divide ground beef into 4 equal portions and form thin patties (about 1/4 inch thick).
Combine flour, salt and pepper on a plate.
Dredge thin patties in the flour mixture.
Meanwhile, heat enough oil to cover the bottom in a cast-iron skillet.
When the oil is sizzling, but not quite smoking, add the patties to the pan.
Cook on each side for just a few minutes to sear the beef and create a browned crust on the burger. (We like our burgers medium-rare, and this doesn't take long.)
While the burgers are cooking, butter rye bread and toast in a non-stick skillet.
When the burgers are fried to your liking, remove from cast-iron skillet and set aside.
Add a little more oil to the pan (if necessary) and saute the onions and mushrooms.
Season with salt and pepper.
Sprinkle in flour and cook about 1 minute.
Stir in beer (or beef broth) and cook until gravy is thickened.
Remove from heat and keep warm.
Place 4 bread slices on a baking sheet and arrange 1 beef patty on each.
Layer a slice of provolone on top of each patty.
Heat in oven for 5-8 minutes, or until cheese is melted and gooey.
Divide mushroom mixture between sandwiches and top with remaining slices of bread. (Yield: 4 sandwiches)