Vanilla Challah French Toast Casserole

Grease a 9x13 inch baking dish with 1 tablespoon of unsalted butter. Cut the 16 ounces of challah bread into 1-inch cubes and place them evenly in the prepared dish.

In a large mixing bowl, whisk together the 6 large eggs, 2 cups whole milk, 1/2 cup heavy cream, 1/4 cup granulated sugar, 1/4 cup brown sugar, 1 tablespoon vanilla extract, 1/2 teaspoon ground cinnamon, and 1/4 teaspoon salt until the mixture is completely smooth.

Pour the egg mixture evenly over the cubed bread in the baking dish. Press down lightly with a spatula to ensure all the bread pieces are submerged and coated. Cover the dish tightly with foil and refrigerate for at least 2 hours, or preferably overnight.

Preheat your oven to 375 degrees F. Remove the casserole from the refrigerator and let it sit at room temperature for 15 minutes while the oven heats. Cut the remaining 1 tablespoon of butter into small pieces and dot them evenly over the top of the casserole.

Bake uncovered for 45 minutes, or until the casserole is puffed, cooked through, and golden brown on top. Let it cool for 5 to 10 minutes before slicing and serving.