Originally Posted by Gravy Queen
I'm in the UK and I have never heard of it.
What recipe is it for and I might be able to see if there is a substitute.
I have, but only in Jane Grigson's book about preserving meat and making pates and terrines. Leaf fat (also called "flead", "flair", or "flay" in parts of the UK) is the sheet of fat forming an interior covering to the loin and enveloping the kidneys. I used to use it in pate and terrine making but I have found it very hard to find in butchers in the north of England (home of such delicacies as black pudding and other arcane mixtures of pig products and offal) and I suspect that nowadays it's stripped off the carcass at the slaughter house and sent to the renderers and the butcher never sees it in his shop.
It does make the best lard so if this is an old recipe it may have stated "leaf lard" to distinguish it from cheaper lard made from all sorts of bits and bobs of waste fat. Much in the same way that recipes used to refer to "best butter" to distinguish fro margarine or butter adulterated with other fats.
I wonder if you could use shredded suet in your pastry. I'm not very good at pastry (warm hands, cold heart as my Mother used to say) so I often use Delia Smith's recipe for suet patry. It doesn't make an elegant pastry but is nice and flaky for steak and kidney pies, fruit pies, etc.