Roll out the puff pastry until a few millimetres thick and place on a lightly oiled (or non-stick) baking tray.
Using a knife, score a border of an inch around the edge and spread a thin layer of patê leaving this border clear.
Finely chop the onion and mushroom before sprinkling over the top of the patê. Next add the chopped nuts and parsley.
Brush the edges of the pastry with a little milk.
Using an oil spray, lightly spray the top of the tart and place in an oven at gas mark 6 for 15-20mins or until the pastry has risen and the mushrooms cooked.
Serve piping hot out of the oven.
Notes
No walnuts in your cupboard?
You can use any nuts you like! We sometimes use hazelnuts.