Add the cashews to a medium bowl. Pour in enough warm water to completely cover the cashews, then soak for at least 2 hours, or overnight. Drain.
Grease 4 4-ounce ramekins with coconut oil and set aside.
Add the cashews to a blender with the water and a pinch of salt. Blend on high speed for 2 minutes, or until very creamy.
In a medium saucepan over medium-low heat, combine the cashew cream, sugar, and vanilla bean seeds. Warm slowly, stirring occasionally, until the sugar is dissolved and the mixture is simmering.
Add the agar agar to the hot water and stir until there are no lumps and the agar agar is fully dissolved.
Pour the agar mixture into the warm cashew cream and whisk to combine. Increase the heat to medium, bring to a gentle boil, and whisk continuously for 3 minutes, until thickened. Remove the cream from the heat and immediately divide between the greased ramekins. Smooth the tops.
Refrigerate for at least 30 minutes, or until ready to serve. (The agar will set at room temperature, but chilling the panna cotta in the fridge will expedite the process.)
When ready to serve, use an offset spatula or butter knife to carefully work around the edges of the ramekins to loosen the panna cotta. Invert onto serving plates and garnish with fresh berries.