Put all ingredients into the bowl of a food processor and whizz until the texture of biscuit crumbs. If your food processor isn't very powerful, it can help to roughly chop the dates first, and give your processor a break every few minutes to stop it over heating.

Tip mixture into a spring form tin and press down firmly, using the back of a spoon or a drinking glass. I used a 23cm (9 inch) tin, you could also use a smaller one - you'll just have a thicker base and topping layer. I didn't line my tin, but if you're nervous about it sticking then go ahead and do that first.

Put the base in the freezer to set until you're ready to pour in the filling.

Preheat oven to 220C (430F) fanbake.

Half your grapefruit and arrange them on a baking tray. Roast for about half an hour, or until softened and with char marks in places.

Remove from oven and set aside until cool enough to handle.

Squeeze grapefruit to obtain ¾ cup of juice. For me, this took three whole grapefruit (six halves). Depending on the size and ripeness of your fruit, you might need more or less.

Drain and rinse the cashews, and add to a high speed blender or food processor.

Add grapefruit juice, and all remaining filling ingredients.

Blend until well combined and completely smooth.

Pour into pre-prepared tin and spread mixture evenly.

Freeze until firm. Allow at least six hours, or better yet, freeze it overnight.

Remove from the freezer and allow to thaw for an hour or so before serving.