1. In a bowl combine the ground beef with 1/2 cup finely chopped onion, the minced garlic and salt and pepper. Form into 4 patties (oblong is the usual Salisbury Steak form). Season the outside well with salt and pepper.
2. In a skillet, cook the patties for about 2 - 3 minutes per side, (you want them rare). Remove from the skillet and set aside.
3. Add the oil to the skillet, when hot add the mushrooms and saute until browned. Add the onion and cook another minute; add the red wine and balsamic, cook, stirring, until the liquid has been absorbed. Add the beef stock; bring to a simmer; return the patties and cook for about 3 minutes spooning the sauce over the patties occasionally. Add the corn starch slurry and cook until thickened. Place one patty on a warmed plate and spoon the sauce over the top. Garnish with parsley, if desired.
Per Serving: 386 Calories; 26g Fat (10g Sat, 11g Mono, 1g Poly); 22g Protein; 9g Carbohydrate; 1g Dietary Fiber; 88mg Cholesterol; 897mg Sodium.