Add flour and salt to the bowl of a food processor fitted with a pastry blade (or sift together into a large mixing bowl)
Add chopped, chilled butter and vegetable fat and pulse briefly until it looks like breadcrumbs (or rub in with your fingers in the mixing bowl)
Add iced water a tablespoonful at a time, pulsing, until the pastry begins to clump together (or with your hands), you may not need all the water, you may need a little more.
Turn out onto a lightly floured surface and bring the soft dough together with your hands. Form a disc, wrap in cling film or baking parchment and chill for at least 20 minutes. Make your filling while the pastry chills.
Lightly grease the flan dish.
On a lightly floured surface roll the pastry out to fit your flan dish.
Drape the pastry over the flan dish and persuade it into place using a small ball of pastry to press it into the edges of your dish.
Chill for a further 20 minutes.
To Make The Quiche Filling
Heat the olive oil in a large frying pan and gently fry the chopped leeks and onions until soft.
Add the mushrooms and continue to cook gently until their juices have evaporated.
Add the garlic and herbs and fry for a further minute until aromatic. Leave to cool.
Preheat oven to 180C/350F.
Whisk together the silken tofu, mustard and nutritional yeast.
Add the tofu mixture to the cooled vegetables and stir to combine.
Add salt and pepper to taste.
Spoon the filling into the prepared pastry case and bake in the preheated oven for about 30 minutes until set on top and the pastry is browned.
Serve warm or at room temperature topped with freshly snipped chives.
Notes
Nutritional information is only an approximate guideline. Calculations will vary according to the ingredients you use and your cooking methods.