This recipe is so delicious, I served it to my family on Christmas morning this past year and it was a big hit. I didn't use the Gran Marnier that time, but I'm sure the addition of that would be great too! It makes around 8 servings, so if you have a large group coming, I would recommend making 2 or making an accompanying dish to go with it. Something with eggs and sausage would be great.
1 cup (2 sticks) unsalted butter
2 cups packed brown sugar
4 tablespoons corn syrup
1 (8 to 9) inch round loaf Challah bread
5 large eggs
1 1/2 cups half and half
1 teaspoon vanilla
1 teaspoon Grand Marnier
1/4 teaspoon salt
In a small heavy saucepan melt butter with butter with brown sugar and corn syrup over moderate heat, stirring, until smooth and pour into a 13 by 9 by 2-inch baking dish. Cut 6 (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, Grand Marnier and salt until combined well and pour evenly over bread. Chill bread mixture, covered, at least 8 hours and up to 1 day.
Preheat oven to 350 degrees F and bring bread mixture to room temperature. Bake uncovered, in middle of oven until puffed and edges are pale golden, 35 to 40 minutes.