Preheat oven to 320F (160°C) and line a 9 or 10 inch spring form pan that is at least 3 inches deep. First grease it with vegan butter or a little oil so the paper sticks. Then draw around the bottom of the cake pan on parchment paper, cut it out and put that in the bottom of the pan. Line the sides of the pan with a long rectangular strip of baking parchment.
Put the digestive biscuits (or graham crackers) into a food processor with the melted butter/coconut oil and blend until well combined and looking like crumbly damp sand. Press very tightly into the bottom of the cake pan to form a thick crust layer. Refrigerate while you make the filling.
Add all of the filling ingredients to a blender and blend until completely smooth. Pour over the crust then sit the pan on a baking tray.
Bake for about 50 minutes or until set well around the edges with a tiny bit of a wobble in the middle. Time will vary depending on your oven and the pan you use.
Allow to cool completely, then refrigerate for at least 4 to 5 hours or overnight. Don't put it in the fridge while hot/warm.
