In a shallow dish, mix together the Panko crumbs and flour. Season with salt and pepper. Place the eggs in a separate dish. Heat oil in a large skillet over medium-high heat. Dip pork steaks in eggs, then coat with the Panko Crumb mixture. Fry 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 water and dissolve the bouillon cube. Simmer for about 20 minutes. Stir together the cornstarch and sour cream; stir into the skillet. Cook over low heat until thickened but do not boil. Spoon over the pork cutlets and serve immediately.