make the caramel sauce
Heat the brown sugar mixture over medium heat and stir until the sugar is melted and the texture is smooth.
layer the bread
add the bread to the bottom of the pan in whatever fashion you see fit.
Make the custard
whisk together the eggs, half and half, vanilla, and Grand Marnier. pour the custard sauce over the sliced bread and let it soak in.
preheat your oven to 350 degrees and then bake the creme brulee French toast casserole about 30 minutes.
serve piping hot or at room temperature