Serve with thick noodles, potatoes, or another German favorite of mine Red Cabbage.
In a shallow dish, mix together the bread crumbs and flour. Season with salt and pepper. Beat the egg in a separate dish with a couple tablespoons of water. Heat oil in a large skillet over medium-high heat. Dip pork steaks in egg, then coat with the bread crumb mixture. (Optional Repeat this process if you want the crust to be thicker.) Fry the breaded pork in the hot oil until browned on both sides and cooked through, about 5 minutes per side.
Remove the pork to a platter and keep warm. Add onion and mushrooms to the skillet and cook until lightly browned. Pour in beef broth and simmer for about 20 minutes to give the broth time to reduce. Stir the cornstarch in some cool water to dissolve then stir into the skillet. When it has thickened, add the sour cream and cook over low heat until hot. Spoon the sour cream mixture over the pork cutlets and serve immediately.