Lightly grease a 13-by-9-inch baking dish. Layer the challah pieces in the dish.
In a large bowl, whisk the eggs, milk, cream, brown sugar, vanilla, 1 teaspoon of the cinnamon, the salt, and nutmeg. Pour the egg mixture over the bread, cover the baking dish with plastic wrap, and refrigerate for at least 2 hours or up to 1 day.
Heat the oven to 375°F and remove the dish from the fridge. In a small bowl, stir the granulated sugar with the remaining 1 teaspoon of the cinnamon. Drizzle the butter evenly over the bread, then sprinkle with the cinnamon-sugar. Bake for 35 to 45 minutes, until puffed and deep golden brown.
Let rest for 10 minutes. Serve with maple syrup, a dusting of powdered sugar, and a topping of fresh berries.
