Lightly grease the cake tin with margarine. Preheat oven to 160C/140C fan/gas 3. Melt the margarine in a saucepan over a low heat. Crush the biscuits to a coarse breadcrumb texture (a food processor works for this, or put them in a plastic bag and bash them up). Add the crushed biscuits to the melted margarine and mix together. Tip this mixture into the cake tin and push it firmly in to get an even base. Bake for 8 minutes – this will help the base keep its shape when cut.

Chop the chocolate roughly into small pieces. Put the tofu into a saucepan and break it up with a spoon. Add the chocolate, and heat very gently. Keep stirring until the chocolate has melted and combined with the tofu. This stage doesn't look very appetising, but it will look better soon! Turn off the heat when the mixture is evenly chocolatey and looking a bit smoother.

Turn the oven to 170C/150C fan/gas 3.5. Tip the tofu & chocolate mixture into a food processor and blitz it until completely smooth (or use a stick blender to blend it in the saucepan). Add the maple syrup and orange essence and blitz a little bit more. Taste the mixture, and add more syrup and/or orange essence if needed.

Pour the mixture over the biscuit base, and smooth it out. Bake for about 25 minutes, or until the topping is beginning to colour and set. Best when left to cool to room temperature, and then refrigerated.