The day before serving, prepare apples and French toast: In large, heavy skillet, melt butter over medium heat. Add apple slices and cook, stirring occasionally, until tender.
Add brown sugar, corn syrup, and cinnamon to apples. Cook stirring, until brown sugar dissolves. Pour apple mixture into 13 by 9 inch baking pan and spread to even layer. Arrange bread slices in one layer on top of apple mixture.
In medium-size bowl, with fork, beat eggs, milk, and vanilla extract until well mixed; pour over bread slices. Cover with plastic wrap and refrigerate overnight.
Next day, heat oven to 375 degrees. Remove plastic wrap from baking pan and bake french toast 30 to 35 minutes or until mixture is firm and bread is golden. Cool in pan 5 minutes. Invert serving tray over French toast and carefully turn both over to unmold so that apple layer is on top. spoon over bread any apple slices or syrup left in pan. Serve and enjoy!