Whisk together cream, egg yolks, and sugar in a 2-qt. saucepan, and cook over medium heat, whisking constantly (so mixture doesn't scorch or scramble), 8 to 10 minutes or until mixture thinly coats back of a wooden spoon. Pour through a fine wire-mesh strainer into a bowl. Stir in apple brandy or bourbon. Add cinnamon stick, if desired. Fill a large bowl with ice. Place bowl containing cream mixture in ice, and let stand, stirring constantly, 30 minutes. Remove cinnamon stick. Cover and chill 1 hour to 3 days.