Grease 9x13 baking dish. Arrange bread cubes evenly in dish.
Whisk eggs, milk, cream, vanilla and sugar in large bowl. Pour over bread.
Press bread down gently to submerge. Cover tightly, refrigerate 4+ hours (overnight best).
For topping: Mix flour, brown sugar, cinnamon and salt. Cut in butter until crumbly. Refrigerate separately.
Preheat oven to 350°F. Sprinkle topping evenly over casserole.
Bake uncovered 45-60 minutes until golden and set (less time for softer texture).
Let stand 5 minutes before serving with maple syrup.