Chop onion and fry gently in a non-stick pan for 10 minutes. Add the tomatoes, vinegar, salt, pepper and sugar. Simmer for 15 minutes
3
Dived pastry into quarters, roll out each square to about 20cm square. Place 2 oz of mushrooms onto each square.
4
Spoon tomato mixture over mushrroms. Bring corners up and overlap at the top. press edges together. Cut a couple of steam slits in the top of pastry and bake for 25 minutes