Mix the instant coffee, cardamom pods, and cinnamon with 50ml of just-boiled water in a small bowl, cover, and leave to infuse for 2 hours.
Pour the double cream and condensed milk into a large bowl and strain in the infused coffee mixture, discarding the spices.
Use an electric whisk to beat everything together until the mixture is thick and the consistency of clotted cream. Scrape into a container then freeze overnight until solid.
Scoop the ice cream into small bowls to serve.