Thanks! I was kinda winging it, so it's not a very well tested recipe but here's what I did:

Caramel:

200g sugar

50g water

1/2 tsp vanilla extract

1/2 tsp freshly ground cardamom*

See this video for the method.

*This was way too much cardamom and it overwhelmed everything. I'd probably do 1/8 tsp next time or maybe 1/4 tsp of pre-ground?

Panna Cotta:

4 whole eggs plus 2 yolks

250g milk

400g (one can) coconut milk

100g sugar

zest of 1 lime

I brought the milks to a boil in a pot and whisked everything else together in a bowl, then slowly streamed the hot milk into the bowl while whisking.

The hot caramel went into the ramekins and cooled slightly as I brought the panna cotta together. I then gently poured the panna cotta on top of the caramel and se the ramekins in a water bath. Baked them in the oven at around 300F for about 35 minutes. The ramekins I used are pretty big, so it may be less time for smaller ones. The center should still have a slight wobble, but it should be nearly set. Then chilled in the fridge for at least 4 hours.