Whisk together half-and-half, milk, apple cider, eggs, sugar, 1/4 tsp. ground cinnamon, salt, and nutmeg in a heavy saucepan. Cook over medium-low heat, whisking constantly, 15 to 20 minutes or until mixture thickens and coats a spoon.
Remove from heat; stir in bourbon, if desired. Top each serving with sweetened whipped cream.
