Bring half a saucepan of water to a boil and boil the 300g cashews for 20 minutes to soften them (you can also soak them in hot water overnight). Discard the soaking water and place them into the food processor with the lemon juice. Blitz until smooth.
Warm up the vegan cream cheese in the microwave for 30 seconds so that it will be easier to blend (if it’s coconut base it’ll soften easily, if it’s tofu-based it may only get a little soft).
Add this vegan cream cheese to the food processor with the vanilla paste, lemon extract and salt then blitz again until smooth. It will be very thick so you may have to scrape down the sides to get it to blend completely smooth.
Mix the agar powder with the sugar so that it is “dispersed” – this prevents clumping. Add the 50ml water to this mix to form a sugary paste. Then add this mixture to a pan with the coconut cream.
Turn on a medium-low heat and bring the cream mixture to a simmer. Stir constantly to prevent the agar from clumping around the edges. Once it starts simmering, stir for another 1 minute and then take off the heat.
Quickly pour this hot cream into the blender with the other ingredients and blitz on high until completely smooth and incorporated.
Pour this cream into the cake tin in on top of the frozen crust and leave it in the fridge to set for at least 3 hours.