Whisk egg yolks and cornstarch together in a medium bowl until light and creamy.

Simmer Milk: In a saucepan over medium heat, combine the cream, milk, sugar, nutmeg and salt. Stir often until mixture reaches a bare simmer.

Temper Eggs: Scoop a ladle-full of the hot milk mixture then slowly drizzle it into the egg mixture, while stirring, to gradually heat the eggs. Repeat with another spoonful of simmering milk.

Combine: Pour egg mixture into saucepan then cook until it comes to a low boil (few bubbles break the surface). Stir constantly, scraping the bottom and sides of the pan. Remove from heat then stir in butter, vanilla, and rum extract.

Chill: pudding into cooled, baked pie shell then place a piece of plastic wrap on the surface of the pudding to keep it from forming a skin. Refrigerate for several hours before serving.

Serve: Slice and serve topped with a dollop of fresh whipped cream and a sprinkle of cinnamon.