- Start by cutting your challah or brioche loaf into roughly 1-inch cubes. Spread the cubes out on a baking sheet and let them sit while you prepare the custard mixture. 
- In a large bowl, whisk together 4 large eggs, 2 cups of milk, 1/2 cup granulated sugar, 1 tablespoon cinnamon, and 1 teaspoon vanilla extract until combined and smooth. 
- Add the cubed bread and 1/2 cup raisins to the custard mixture. Gently fold everything together, making sure all the bread cubes are coated with the custard. 
- Butter a 9x13-inch baking dish generously to prevent sticking. Pour the bread and custard mixture into the dish, spreading it out evenly. 
- Cover the dish with plastic wrap and refrigerate for at least 2 hours or overnight to allow the bread to soak up the custard. 
- Preheat your oven to 350°F (175°C). Remove the baking dish from the fridge and bake uncovered for 45-50 minutes, or until the top is golden and the custard is set. 
- Once baked, drizzle with 1/4 cup pure maple syrup and sprinkle powdered sugar over the top if desired. Serve warm.