Grease a 6” springform or pie dish, making sure it fits inside your pressure cooker pot. If you don't have a high-powered blender, you may want to soak the cashews in boiled water for a few minutes before pureeing, to make sure you get the smoothest texture.

Pulse one cup of the dates and the oats together in a food processor until it makes a sticky mixture. Press this into the base of the pan.

Puree the other quarter-cup of the dates (or you could use 1/4 cup unrefined sugar), cashews, blueberries, and lemon/lime juice with 3/4 cup water and a pinch of salt in a blender on high, until smooth and creamy (approx one minute). You'll probably have to stop a couple of times to push the mixture down the sides. Pour this over the pie base. Cover the pie dish with tin foil, and use foil or silicone helper handles.

Put a trivet in the bottom of the pressure cooker, add about a cup of water or enough to cover the bottom of the pot but not go higher than the trivet. Lower the pan down onto the trivet using the helper handles.

Close and lock the lid, ensure the pressure valve is sealed, then select high pressure, and set the time for 6 minutes. Allow the pressure to release naturally.

Once all the pressure has released, unlock the lid, and allow to cool for a few minutes before carefully lifting the pan out with oven mitts.

Let the cake cool to room temperature, or chill in the fridge, until cooled and set.