Preheat the oven to 190ºC (fan)/375ºF/Gas Mark 5 and line a large baking tray with parchment.
Using a large dinner plate and on a floured surface, cut one of the pastry sheets around the shape of the plate.
Take the next pastry sheet and again cut around the shape of the plate but this time leave 2cm of extra pastry around the edge.
Place the smaller circle on the lined baking tray and set aside.
Fry the onions in a little vegan butter until soft and golden.
Add the leeks and fry for a further 5 minutes.
Add the mushrooms and fry for another 5 minutes.
Add the garlic and the cayenne pepper and fry for a minute.
Remove from the heat and stir through the flour until all the vegetables have been covered.
Place back onto the heat and then stir through the tomato puree and add all of the other ingredients apart from the pre-cooked quinoa/lentils and soya milk.
Allow the mixture to simmer, stirring regularly, for around 15-20 minutes.
Add the quinoa or lentils to the mix and stir through. The consistency should be thick but not too thick. Add a little more stock if necessary (you don’t want it to be runny though).
Transfer the mixture onto the bottom layer of pastry and leave a good couple of inches of pastry free around the edge.
Cover with the bigger circle of pastry and seal the edges with your fingers. Brush the edges with some oil.
Brush the pastry with soya milk.
To create the sun pattern, make a tiny hole in the centre and then score wavy lines from the centre to the outer edge of the pastry using a sharp knife.
Place in the oven and bake for 25-30 minutes or until crisp and golden.