Add 1/2 cup of defrosted raspberries together with the coconut milk in a blender and blend until smooth. Place a nut milk bag over a pot and pour in the raspberry-coconut mixture, squeeze to remove the harder bits of the raspberries.
Whisk in the agar powder and sugar and bring it to a boil. Let it simmer for 2-3 minutes, then fill the mixture into small glass or porcelain containers**.
Let them sit in the fridge overnight.
For the raspberry sauce simply simmer the defrosted raspberries together with the sugar in a small pot and mash the raspberries a bit.
To serve, go around the edges of the panna cotta with a knife until you can take it out of the form. Top with the warm raspberry sauce.