1In shallow dish, stir milk, Bisquick mix, vanilla and eggs with fork or whisk until blended. In each slice of bread, cut 3-inch pocket through top crust. Spread about 1 teaspoon mustard in each pocket. Place 1 oz ham and 1/4 cup cheese in each pocket.
2Heat griddle or skillet over medium heat (350°F); melt butter on griddle. Dip bread in egg mixture, coating both sides. Place bread on hot griddle; cook about 5 minutes, turning once, until golden brown.
3Cut French toast in half diagonally; sprinkle with powdered sugar.