Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish with butter or cooking spray.
In a large mixing bowl, whisk together the eggnog, eggs, vanilla extract, cinnamon, nutmeg, brown sugar, and maple syrup until smooth.
Add the cubed bread to the bowl and gently toss to coat the bread thoroughly in the eggnog mixture. If using pecans, fold them in now.
Pour the mixture into the prepared baking dish, spreading it evenly. Press down gently to make sure all the bread is submerged in the liquid.
Cover the baking dish with foil and let it sit in the refrigerator for at least 30 minutes or up to overnight to allow the bread to soak up the custard.
When ready to bake, remove the foil and bake in the preheated oven for 30-35 minutes, or until the top is golden brown and the center is set.
Allow the French toast bake to cool for a few minutes before dusting with powdered sugar. Serve warm drizzled with additional maple syrup.
Notes
Serve slices on individual plates and garnish with a sprinkle of powdered sugar and a drizzle of maple syrup. Add a sprig of mint for a pop of color!