Boil 2 cups of water in a kettle. Wrap the hibiscus flowers in cheesecloth and stir, along with the maple syrup and 2 cups boiling water into a medium pot. Place the agar-agar flakes in the pot and let sit at least 20 minutes.
While tea is seeping, rough cut your pistachios.
Remove the hibiscus flowers and bring to a boil, and simmer for 5 minutes, or until the agar dissolves. Pour into a glass measuring cup and let it cool down.
Pour into 4 small glasses or teacups. Finish cooling process in the refrigerator, at least 2 hours. In a large bowl, whip the heavy cream and vanilla until thick.
Dollop the cream over the hibiscus gelee with a sprinkling of pistachios and enjoy!