Preheat the oven to 170oC/ Gas Mark 5. Line a rectangular or round baking tin (approx 20x30cm (8x12in) or 24cm 9in) diameter or similar) with Bacofoil® Non-Stick Baking Paper (this will ensure the pastry doesn’t stick). Make sure the sides are about 2cm (3⁄4in) deep.
To make the pastry, combine the flour, almonds and linseed in a bowl. Mix the brown rice syrup into the melted coconut oil, then drizzle it over the flour mixture. Use a blunt knife or palette knife to chop through and mix until it becomes evenly clumpy. Add 2 tbsp cold water and mix again with the knife until the mixture starts to clump together (add another tablespoon of water if required).
Press the crumb into the lined tin so that it evenly covers the base and sides. Prick the surface with a fork. Scrunch up another piece of Bacofoil® Non-Stick Baking Paper, then unfold and place gently on top of the pastry base. Fill with baking beans or raw rice to weigh down the paper and pastry. Bake for 20 minutes or until pale golden brown. Leave to cool for a few minutes, then carefully lift out the beans and allow the pastry to cool fully.
While the base is cooling, make the filling. Break the chocolate into a heatproof bowl, then add the vanilla and rice syrup. Heat the coconut milk in a small saucepan until hot, but not boiling, then pour over the chocolate and stir until everything is melted and well mixed. Pour into the pastry case and smooth over. Allow to cool, then chill until set.
Decorate with toasted coconut flakes and chopped pistachios and cut into small slices to serve.