01 - Grease a 9x13-inch baking dish. Distribute the cubed brioche uniformly within the prepared dish.
02 - In a capacious bowl, thoroughly whisk together the eggnog, eggs, granulated sugar, cinnamon, nutmeg, vanilla extract, and salt until a homogenous consistency is achieved.
03 - Evenly decant the custard mixture over the bread cubes. Employ gentle pressure to facilitate optimal liquid absorption by the bread.
04 - Cover the dish and refrigerate for a minimum of 30 minutes, or preferably overnight, to enhance textural development.
05 - Preheat your oven to 350°F (175°C).
06 - In a separate small bowl, combine the brown sugar, cinnamon, pecans (if utilizing), and melted butter. Mix until well incorporated.
07 - Evenly sprinkle the prepared topping mixture over the custard-soaked bread. Commit to the preheated oven and bake for 40 to 45 minutes, or until the casserole is visibly puffed, golden brown, and the interior is set.
08 - Allow the casserole to cool for 10 minutes post-baking. Serve warm, garnished with maple syrup and a dusting of powdered sugar, if desired.