First Step: Prepare the Bread

1. Slice the Bread: Begin by slicing the challah bread into 1-inch thick slices. If the bread is fresh, let it sit out for a few hours or overnight to dry slightly. Stale bread works best as it absorbs the custard without becoming mushy.
2. Cut the Bread into Cubes: After slicing the bread, cut each slice into cubes, about 1 to 1.5 inches in size. This will make it easier for the bread to soak up the custard mixture.

Second Step: Prepare the Custard Mixture

1. Whisk the Eggs and Milk: In a large mixing bowl, whisk together the eggs, whole milk, heavy cream, and vanilla extract until smooth. The eggs and milk create the custard that will soak into the bread cubes.
2. Add Sugar and Spices: Add the brown sugar, granulated sugar, ground cinnamon, ground nutmeg, and a pinch of salt to the mixture. Whisk until everything is fully incorporated and the sugar has dissolved.
3. Pour Over the Bread: Place the cubed bread in a large greased baking dish (9×13 inches). Pour the custard mixture evenly over the bread cubes, making sure each piece is soaked with the custard. Press the bread gently into the custard to ensure it’s fully submerged.

Third Step: Chill the Casserole

1. Cover and Refrigerate: Cover the baking dish with plastic wrap or aluminum foil and refrigerate for at least 1 hour or overnight. This step allows the bread to soak up the custard mixture, resulting in a richer, more flavorful casserole.

Fourth Step: Bake the Casserole

1. Preheat the Oven: Preheat your oven to 350°F (175°C).
2. Prepare the Topping: In a small bowl, combine the melted butter, granulated sugar, and a sprinkle of cinnamon. Drizzle this mixture over the top of the casserole before baking. This will create a golden, slightly crispy top as the casserole bakes.
3. Bake: Place the casserole in the preheated oven and bake for 45-50 minutes, or until the top is golden brown and the center is set. You can insert a knife into the center to check; it should come out clean when the casserole is done.

Final Step: Serve and Enjoy

1. Let it Cool Slightly: Once the casserole is done baking, remove it from the oven and let it cool for a few minutes before slicing.
2. Top with Your Favorite Toppings: Serve the casserole warm with your choice of maple syrup, fresh berries, whipped cream, and a dusting of powdered sugar. You can also add chopped nuts for extra crunch.