Pre soaking the cashews overnight will help soften them, but if you have a high speed blender and don't have the time or inclination to pre-soak them then you can blend them as is with the water. Blend for 3 minutes or until completely broken down and you have a smooth creamy milk.
Melt the cocoa butter. The microwave is great for this. Microwave it in 30 second bursts, stirring each time, until melted. Otherwise you can melt the cocoa butter using the double boiler method. Once melted turn the blender on, and once the liquid has settled a bit use the spout at the top to slowly pour in the cocoa butter. Replace the spout and blend for 2 minutes.
Add the strawberries and sugar and blend until completely smooth. Pour the mixture into a small saucepan and add the agar agar powder and whisk to combine. Leave for 10 to 15 minutes.
Place the saucepan over a medium low heat and bring to a simmer. Reduce the heat to its lowest setting and simmer for 5 minutes, whisking every now and then.
Divide the panna cotta mixture between your serving dishes. I used a combination of silicone bundt moulds and glasses. Whatever you have will be fine. Leave on the bench for 5 minutes before refrigerating until completely set and chilled. Allow about 2 to 3 hours for this.
Serve with your favourite accompaniments.
If you have agar flakes use 1 tbs of flakes for every 1 tsp of powder. Agar agar powder is commonly found in health food shops here in Australia. Outside Australia you can find it here on Amazon.