Heat the Whole milk, Heavy Cream, and Mascarpone on low heat. Stir Add the Espresso powder, and continue stirring until the mixture just starts to bubble on the edges. DO NOT BOIL Remove from heat (If you have a thermometer, you want the temperature to reach approximately 180 degrees F).
Prepare the egg mixture
In a separate bowl combine your egg yolks and sugar
Final Mix
Return the milk mixture to low heat, and stir in the egg yolk/sugar mixture. Again DO NOT BOIL. Keep stirring until fully blended, and then remove from heat
Let the Gelato cool for 5 minutes
Add the spiced Rum, and Cocoa. Stir until blended
Pour the Gelato liquid into 2 Ninja Creami pints. Freeze for at least 24 hours.
Ninja Creami Magic
Remove a pint of Gelato from the freezer, and remove the lid
Place the pint in the Ninja outer bowl with the paddle lid
Turn the Ninja Creami on, and place the bowl in the locked-in upright position. Push the Gelato button