Prepare a 9 x 13 (or similar size) baking dish with non-stick spray. Cut the loaf of bread into bite-sized cubes and place them in the pan in an even layer.
In a mixing bowl add the eggs, milk, cream, sugar, nutmeg, and vanilla and whisk to combine. Pour the mixture over the bread cubes and use a large spoon to mix and coat all of the pieces. Cover the dish with plastic wrap and refrigerate overnight.
The next morning, preheat the oven to 350°F. Take the pan out of the fridge and give the bread another gentle mix so that the egg mixture gets evenly distributed.
While the oven is preheating, combine the flour, brown sugar, cinnamon, salt, and cubed cold butter in a mixing bowl. Use a pastry cutter, a fork, or your hands to combine the mixture into a crumble. Mix in the pecans and spread out evenly over the top of the casserole.
Bake for 45 minutes. Remove the pan from the oven and serve with maple syrup. Refrigerate any leftovers covered for 1-2 days.