Thank you all--especially Horatio and frenchfancy, as I was aiming at something savoury. Great suggestions, especially as I had a batch of home made tomato sauce in the fridge waiting to be used up. This could be a new family favourite!
mrspremise, you are right to ask, as the recipe that needs it is a really good one! It is Ham Pivithier, and it's a Lindsay Bareham one from The Times. You roll out some ready made flaky pastry, twice as long as wide, trim the edges, and then imagine it folded in half and on one side only, make some slits. Place the pastry on a greased baking tray. On the side you have not made some slits in, place some leeks that you have chopped and sauteed (and it says, allowed to cool though I never have time for that!). On top of the leeks, place pulled ham hock (packet from Sains or Waitrose), having picked out any gristly bits. On top of the ham, dollops of mascarpone (about half the tub), then on top of that, chopped parsley. Fold over the other half of the pastry, the side that has the slits in (this will then be on top), seal the edges together with beaten egg and use a fork to crimp. Brush top with beaten egg. Bake for 25 mins at 220 deg. It's very good!
Difficult to describe how you cut the pastry without a diagram but if you have done something similar before you will get the gist!