Gently muddle spices together, just enough to break open cardamom pods and lightly crush peppercorns and fennel seed.
Heat cream in a small sauce pan until not quite simmering.
Remove from heat, add spices and allow to soak for 1 hour. Strain through cheese cloth – squeezing to extract all the flavor.
Whisk egg yolks and sugar in a metal bowl over a pot of simmering water until pale and syrupy. Continue beating until mixture is hot to the touch (120F).
Remove from heat. Whisk in cream in a steady stream.
Cover and allow to cool in the fridge for at least 2 hours.
Fold in ½ c rhubarb and all of liquid and churn according to your ice cream maker.
When ice cream is almost done (holds its shape), add remaining rhubarb and churn for a further 5 minutes.
Scrape out of ice cream maker into storage containers and freeze until firm.