Slice bread into 1-inch cubes. Arrange cubes in a buttered 9 by 13-inch baking dish.
In a large bowl, combine the eggs, half-and-half, milk, syrup, vanilla, nutmeg, and salt and whisk until blended but not too bubbly. Pour mixture over the bread slices, making sure all are covered evenly with the milk-egg mixture. Cover with foil or plastic wrap and refrigerate overnight.
Beat the cream cheese with bourbon (if using), milk, sugar, and lemon juice until smooth. Store in the fridge until serving.
The next day, preheat oven to 350 degrees. Bake casserole for 40-45 minutes.
Serve with glaze (to thin glaze out, simply whisk with a fork for a minute or add a slash more bourbon or milk.)
Notes
I like to use whole wheat bread for a dose of whole grains, but any thick bread will work for this casserole. Or make gluten-free eggnog french toast by using gluten-free bread.
To make this dairy-free eggnog french toast, substiute the milk and half-and-half for coconut milk or almond milk. And grease the casserole dish with coconut oil instead of butter.
It is crucial to use freshly grated nutmeg (whole nutmeg grated with microplane) instead of dried nutmeg for the best flavor in this Eggnog Breakfast Casserole.
If you would like to have the flavor of bourbon without the alcohol content, add the tablespoon of bourbon to the egg custard. The alcohol will bake off and just the flavor of bourbon will remain.
You can also make this in individual 1 cup casserole dishes. Just evenly divide among 12 1-cup ramekins that have been greased and adjust the baking time to 30 minutes.