In a bowl whisk together eggs, half-and-half, vanilla, Grand Mariner, and salt until combined well. Pour evenly over the bread. Cover and chill bread mixture for at least 8 hours or up to one day.
Preheat oven to 350°. Bring bread to room temperature. Bake bread mixture uncovered in the middle of he oven until puffed and edges are pale golden brown - approximately 35 - 40 minutes. Serve Hot French Toast immediately.