Preheat the oven to 180°C/160°C fan/350°F/gas mark 4.
Place the biscuits in a food processor and blitz until very finely crushed. Alternatively, place them in a sealable freezer bag wrapped in a tea towel and bash them with a rolling pin.
Tip the crushed biscuits into a bowl and mix in the melted vegan butter. It should resemble wet sand.
Tip the biscuit mixture into a 23-25cm/9-10in loose bottomed tart tin and press it evenly across the base and up the sides. Use the base of a glass to pack it down really firmly.
Bake the base for 10 minutes then set aside to cool.
To make the filling, place the lime juice, coconut cream, silken tofu, cornflour, sugar and a pinch of salt in a blender and blitz until smooth.
Pour the mixture into a saucepan and stir in the lime zest. Heat, whisking constantly, until the mixtre comes up to a boil and thickens.
Pour it into the prepared biscuit base and spread it level. Refrigerate for at least 4 hours, preferably overnight, until set.
Just before serving, top with coconut whipped cream and lime zest if you like.