Rumchata Eggnog

Make cinnamon-sugar rim: Combine cinnamon and sugar on a shallow plate. Moisten the rim of each glass with water and dip into the cinnamon sugar. Set aside. Make egg nog: In a large saucepan, whisk egg yolks and sugar to combine. Add milk, nutmeg, cinnamon, and vanilla, and turn on heat to medium-low. Cook for about 10 minutes, or until mixture is thick enough to coat the back of a spoon. Do not boil. (If using a candy thermometer, the mixture should reach 160 degrees F.) Remove from heat, stirring in heavy cream and RumChata. Refrigerate until chilled. When ready to serve, pour into cups and sprinkle with additional nutmeg. Garnish with cinnamon sticks if desired.