Prep 20 mins
Cook 40 mins
- Pre-heat oven to 450 degrees.
- Roll out the pastry into a thin oblong and place on a baking sheet.
- Fry the onion in butter until it softens then add the mushrooms and cook for a further few minutes.
- Add the tuna, egg, lemon juice and capers: season to taste.
- Put the mixture on the center of the pastry, damp edges, and fold over, first the top and bottom and then the sides.
- Press edges well together.
- Score a couple of times across the top, brush with milk and place in the pre-heated oven for 15 minutes.
- Reduce the oven temperature to 400 degrees and cook for a further 15 minutes.