In a shallow bowl, whisk together eggnog, eggs, dark rum (if using), vanilla extract, ground cinnamon, and ground nutmeg until smooth.

Slice your bread into 3/4-inch thick slices and lay them on a clean surface.

Heat a large skillet over medium-high heat and add butter until melted and frothy.

Dip each slice of bread into the custard mixture, coating both sides for 1-2 seconds, then cook in the skillet for 2-3 minutes on each side until golden-brown.

Transfer cooked slices to a baking sheet in a preheated oven at 200°F to keep warm while cooking remaining slices.

Plate the French toast and top with whipped cream and maple syrup before serving.