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 damp 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 curd, heat the cranberries, sugar, orange juice and zest, lemon juice and spices in a large pan until simmering. Simmer gently for 5-10 minutes until the cranberries have softened and burst.
Transfer the mixture to a blender and blend until very smooth.
Use a silicone spatula or the back of a spoon to scrape the cranberry mixture through a fine mesh sieve back into the saucepan.
Mix the cornstarch and milk together and whisk into the cranberry mixture. Return the pan to the heat and cook until it comes to the boil and thickens. Once boiling, continue to cook for 30 seconds then remove the pan from the heat.
Add the vegan butter and stir until melted and fully combined. The mixture may look split at first but keep stirring and it will come together.
Pour the curd into the baked biscuit base and spread it level. Allow to cool slightly then refrigerate for at least 4 hours until set.