In a small heavy saucepan melt butter with brown sugar and corn syrup over moderate heat, stirring until smooth, and pour into a 13x9x2 inch baking dish. Cut six 1 inch thick slices from center portion of bread, reserving ends for another use, and trim crusts. Arrange bread slices in one layer in baking dish, squeezing them slightly to fit.
In a bowl whisk together eggs, half and half, vanilla, Triple sec, and salt until combined well and pour evenly over bread. Chill bread mixture, covered at least 8 hours and up to a day.
Preheat oven to 350 degrees and bring bread to room temperature
Bake bread mixture, uncovered, in middle of oven until puffed and edges are golden, 30-40 minutes