Combine the brown sugar, corn syrup and butter in a small saucepan.
Cook over medium heat 5 minutes or until mixture is bubbly, stirring constantly.
Pour mixture evenly into a 13 x 9-inch baking dish coated with cooking spray.
Arrange challah bread slices in a single layer over syrup in dish.
Combine milk, flour, vanilla, salt and vanilla in a large bowl, stirring with a whisk.
Pour egg mixture over challah.
Cover and refrigerate for at least 8 hours or overnight.
Preheat oven to 350°.
Combine 2 tablespoons granulated sugar and cinnamon.
Sprinkle evenly over bread.
Bake at 350° for 50 minutes or until golden.
Let stand for 5 minutes before serving.
Sprinkle with powdered sugar, if desired.