Overnight French Toast with Cinnamon Streusel

Name: Overnight French Toast with Cinnamon Streusel
Ingredients: 1 (1-pound) unsliced loaf brioche or challah bread; Cooking spray or butter, for the baking dish; 8 large eggs; 2 cups half-and-half; 1/3 cup maple syrup, plus more for serving; 1 tablespoon vanilla extract; 1/4 teaspoon kosher salt; Powdered sugar, for serving (optional); 4 tablespoons (1/2 stick) unsalted butter; 2/3 cup all-purpose flour; 1/4 cup packed light or dark brown sugar; 2 tablespoons granulated sugar; 1/2 teaspoon ground cinnamon; 1/4 teaspoon freshly grated or ground nutmeg