Melt butter, add brown sugar and corn syrup. Combine well, Spray 9 x 13 pan Slice bread into 3/4 to 1" thick slices. Pour butter mixture into baking dish, and arrange slices flat in butter mixture, squeeze to fit in. In blender (or bowl) mix eggs, milk and vanilla. Pour over bread slices, covering completely. Cover and refrigerate overnight. Uncover and bake in preheated 350 degree oven for 30 minutes or until golden brown. Dust with powedered sugar. Serve right from baking dish. Makes 6-8 servings.