Heat the cream and stir in the cinnamon. When the mixture starts to boil, remove from heat and set aside to infuse for two hours. In the meantime chop and toast the walnuts.
Beat egg yolks and sugar together until smooth and creamy.
Reheat the cinnamon cream and slowly add to the egg yolks and sugar mixture to temper.
Pour the tempered egg mixture back into the cinnamon cream and stir over medium heat until it thickens enough for the spoon to leave a trail.
Remove from heat and strain into a bowl. Stir in the vanilla and calvados.
Refrigerate overnight.
Churn according to your ice cream machine manufacturer's instructions.
Add the walnuts.
Return to fridge for a couple of hours. Enjoy!