Combine the egg nog, rum or bourbon (if using), milk, eggs, cinnamon, nutmeg, and vanilla extract. Whisk until the eggs and milk are completely combined with the egg nog.
In a large skillet or griddle over medium heat, melt about 1 tsp of ghee per toast slice.
Dunk the bread slices into the egg nog mixture and allow to soak for 10-15 seconds per side (more or less depending on how you like your toast - though the longer it soaks, the more batter you'll need). Place in the skillet and cook until lightly golden brown on each side - about 2 to 3 minutes per side.
Serve topped with maple syrup and fresh whipped cream.