In a large, shallow bowl, whisk together the eggnog, eggs, cinnamon and vanilla.
Heat a skillet to medium low. Melt butter, coating entire skillet.
Dip one slice of bread at a time into the eggnog mixture, being sure to coat each side of the bread thoroughly. Allow excess to drip off back into the bowl.
Place the prepared bread slices into the preheated skillet, and cook, turning once, until golden brown on each side.
Serve warm with powdered sugar, maple syrup or creamy eggnog syrup.