Oooh haven't made one of those in years owing to the lack of good ham. I tend to make chicken and mushroom pie and kind of make it up as I go along but it usually has peas in it as well - I do like to add lots of veg to my meat pies, it's cheaper. Onions go in, some kind of sauce from white sauce to thickened gravy depending on what I feel like. Some herbs perhaps.