Seed the cardamom pods and discard the shells.
In a small saucepan combine the coconut milk, cardamom seeds, sugar and vanilla extract and set on medium heat, stirring to dissolve the sugar.
When the sugar has dissolved, stop stirring and sprinkle the agar agar flakes all over the surface of the coconut milk mixture. Set the heat on medium-high and let cook without stirring until it starts boiling. The agar agar flakes will stay on the surface and not sink.
When the milk starts boiling lower the heat to medium again, and stir. Let simmer for about 10-15 minutes, until the agar agar flakes will dissolve and the coconut milk mixture will slightly thicken. Stir from time to time.
Remove from the heat and pour the panna cotta mixture into 2 moulds filtering through a sieve in order to retain cardamom seeds and agar agar leftovers.
Let cool to room temperature and then transfer to the fridge. This panna cotta requires about 2 hours of resting time in order to harden.
Remove the panna cotta from the moulds and serve with a sprinkle of ground pistachios (optional).
If using ground cardamom, sub the 10 pods for 1/3 tsp of the ground version of the spice.