Begin by cubing your challah or brioche bread into 1-inch pieces and set them aside in a large mixing bowl.

In a separate large bowl, whisk together eggnog, milk, eggs, sugar, vanilla extract, and a pinch each of cinnamon, nutmeg, and salt until smooth.

Gently fold the cubed bread into the custard mixture, along with golden raisins if desired. Let this mixture soak for at least 30 minutes.

Preheat your oven to 350°F (175°C) and prepare a greased 9x13 inch baking dish.

Pour the soaked bread mixture into the prepared baking dish, spreading it out evenly. Top with turbinado sugar, cinnamon, and nutmeg.

Bake for approximately 45-50 minutes, until the top is golden and a knife comes out clean.

While baking, prepare the rum-butter syrup by melting butter in a saucepan, stirring in maple syrup and rum until combined.

Once baked, let cool slightly before slicing, and drizzle each serving with warm rum-butter syrup.