PREPARATION
To toast bread: Spread the bread slices out over two baking sheets. Bake at 325 degrees F until bread is dry and golden, about 14 to 16 minutes, rotating pans every 6 minutes. Remove from oven and let cool completely.
Lightly cover a 13×9-inch pan with non-stick spray. Line the pan with slices of bread; alternating with pear slices in between bread slices; set aside.
In a large bowl whisk together eggs then pour in milk, heavy cream, Grand Marnier, sugar, vanilla extract, cinnamon and until combined. Pour the mixture over the bread and press down on the bread lightly to submerge. Sprinkle cranberries on top.
To make the topping, stir together all ingredients.
Cover and store the topping and casserole separately overnight.
To assemble, unwrap the casserole and sprinkle the topping evenly over the top. Transfer the casserole to the oven and bake at 350 degrees F and bake until casserole is puffed and golden, about 1 hour.