Prepare the pistachios by soaking them. Add them to a large bowl, cover with water and soak for 4 hour (or soak in boiled water for 1 hour). Rinse the pistachios with clean water and remove as much of the skins as possible. They should coming off easily using your fingers as the water will have loosened them
Preheat your oven to 175°C (350°F).
Lightly grease the base and sides of a 9.5" tart tin with some oil or vegan butter.
For the crust, add the pistachios to your food processor and blitz for a minute or so. Add in the remaining crust ingredients and blend until the ingredients stick together to form a dough.
Evenly press the dough half of the dough into the sides of the tart tin first, then press the remaining dough into the base of the tin. With a fork, gently prick the dough several times.
Bake the crust for 12-15 minutes until slightly browned, then allow to cool (do not remove the tart from the tin).
For the filling, melt the vegan white chocolate over a double boiler. Add the melted white chocolate to your blender along with all the other ingredients for the filling. Blend for several minutes until completely smooth and creamy.
Pour the filling into the cooled tart crust and use a spatula to smooth out the surface. Place in the fridge to set for 6 hours, or preferably overnight.
Once set, garnish with some more melted white chocolate, chopped pistachios and fresh mint leaves.