Instructions

• Spray a 9x13-inch baking dish with nonstick spray and set aside.
• Cut the 12 slices of Challah into 1-inch pieces. Place half of the bread pieces in an even layer in the prepared baking dish.
• Cut the two 8-ounce packages of cream cheese (or mascarpone) into small cubes or scoop into small mounds and distribute them evenly over the first layer of bread.
• Sprinkle 1 cup fresh or frozen blueberries (or a little more, if desired) over the cream cheese. Top with the remaining bread pieces, spreading them into an even layer.
• In a large bowl, whisk together 12 large eggs, 2 cups milk, 1 teaspoon vanilla extract, and 1/3 cup maple syrup until well combined. Pour the egg mixture evenly over the bread and cream cheese so the bread is mostly submerged. Press gently on the bread to help it absorb the liquid.
• Cover the dish tightly with plastic wrap and refrigerate overnight (at least 6–8 hours). If you want the bread to absorb more liquid, place a plate or other weight on top of the plastic wrap to help press the bread down.
• The next morning, remove the baking dish from the refrigerator 30 minutes before baking. Preheat the oven to 350°F. Remove the plastic wrap, then cover the dish with foil and bake for 30 minutes.
• Remove the foil and bake an additional 25–30 minutes, until the center is set and the top is golden. Let the casserole rest 5–10 minutes before serving.
• While the casserole is baking or after you remove it from the oven, make the blueberry sauce: In a medium saucepan, whisk together 1 cup granulated sugar and 2 tablespoons cornstarch. Add 1 cup water and whisk until smooth.
• Bring the sugar-cornstarch mixture to a boil over medium heat, stirring constantly. Boil and stir for about 3 minutes.
• Stir in 1 cup fresh blueberries and reduce the heat to low. Simmer about 10 minutes, stirring occasionally, until the blueberries begin to pop and the sauce thickens.
• Stir in 1 tablespoon butter until melted. Serve the French toast warm with the warm blueberry sauce spooned over individual servings.