Sift the flour, icing sugar, cacoa powder and salt into a mixing bowl.
Add in the chopped vegan butter and work into the dry mix until crumbly.
Add the cold water and compress into a ball. Chill in the fridge for 30 minutes.
Pre-heat the oven to 200C.
Scatter flour on a work surface, remove the pastry from the fridge and roll out to a thickness of 4mm.
Spray your tart tin with baking spray (or rub it with butter) and a light dusting of flour.
Pick up the pastry using a rolling pin and drape over the tart tin. Press the pastry against the tart tin all the way around and cut off the excess.
Place parchment into the tart tin with baking beads or dry lentils/rice and blind-bake for 25 minutes. Remove the baking beads and bake for a further 10 minutes.
Take the tart case out of the oven to chill while you work on the fillings.