Marinate the beef for 1 hour in 1/3 cup of the wine.
Heat the olive oil in a large frying pan over medium-high heat. Add the mushrooms and onion and cook until golden about 5 - 7 minutes.
Add the beef and remaining wine and cook until the wine has reduced by half.
In a bowl combine the French seasoning, cornstarch, beef stock, salt and pepper and stir vigorously to blend. Reduce heat to medium - low and pour slowly into the pan, stirring frequently until sauce thickens about 2 -3 minutes.