Grease a 9x13-inch glass baking dish with butter or nonstick spray.
butter or nonstick spray
In a large mixing bowl, whisk together eggs, milk, sugar, vanilla, cinnamon and salt until well blended.
8 large eggs, 2 cups milk, 1 tbsp vanilla extract, 1 tsp ground cinnamon, ¼ tsp salt, ¼ cup granulated sugar
Dip bread slices, one at a time, into egg mixture, allowing to soak for 5-10 seconds per side.
1 loaf challah or brioche bread, cut into 1-inch slices
Arrange soaked bread slices in prepared baking dish, making sure they don't overlap.
Pour any remaining egg mixture evenly over the top.
Cover with foil and refrigerate overnight for best flavor (optional).
When ready to bake, preheat oven to 400°F.
Bake covered with foil for 20 minutes. Remove foil and continue baking 15-20 minutes more until puffed and golden brown.
Let cool 5-10 minutes before serving with desired toppings.