Spray a 9x13 inch baking dish with cooking spray to coat well. Arrange sliced challah in the baking dish, allowing them to overlap. 2. In a large bowl, combine the eggs, half and half, milk, sugar, vanilla, cinnamon, nutmeg and salt and beat with a whisk until blended but not too bubbly. Pour mixture over the bread slices, making sure all are covered evenly with the milk-egg mixture. Spoon some of the mixture in between the slices. Cover with foil and refrigerate overnight. 3. The next day, preheat oven to 350 degrees F. 4. Prepare praline topping by combining all ingredients in a medium bowl and mixing well. Spread praline topping evenly over the bread and bake for 40 minutes, until puffed and lightly golden. Serve with maple syrup.