Using a whisk, mix the coconut milk well with the birch sugar, vanilla seeds and agar-agar in a small pan. Bring to the boil, then simmer for 2-3 mins., stirring continuously. Place into 4 small glasses or ramekins (each approx. 125 ml), allow to cool a little. Cover and refrigerate for approx. 3 hr.
Persimmon cream and serving
Cut the persimmon into quarters using a sharp knife and carefully scrape the flesh out into a mixer bowl. Add the cardamom, and purée using a hand blender.
To serve, Carefully slide the tip of a knife around the edges of the panna cotta. Briefly dip the glasses/ramekins in hot water and turn out the panna cotta onto plates. Distribute the persimmon cream evenly over each panna cotta, and decorate with pistachios.