Rub margarine into flour, mixing well. Add salt and then just enough water to bind the mixture to a stiff dough, cover with cling film and leave in the fridge for an hour.
Roll the dough, cut into four even sized squares, placing them onto a lightly greased baking sheet.
Melt the margarine and gently fry the vegetables for 5 minutes. Add mushrooms and spinach, cover pan and cook on a low heat for 10 minutes, or until vegetables are tender, add herbs and yeast extract and season.
Divide the mixture between the squares draining first if necessary, crimping the edges with water, fold across diagonally and press firmly to seal.
Bake in pre heated oven at 200°C for 20 minutes or until golden.