Remember that episode of Friends where Rachel mistakenly adds mince, sautéed with peas and onions, to her trifle? Her reasoning goes something like this - 'The beef? Yeah, that was weird to me, too. But then, y’know, I thought “well, there’s mincemeat pie,” I mean that’s an English dessert, these people just put very strange things in their food.'
Well up to the age about 15 I also thought mince pies where a savoury, meaty, peculiarly English treat. Despite my mother's huge anglophile tendencies she never made mince pies and I don't think I ever tried one until I moved to London, got a job and experienced my first office Christmas party.
It's not such a silly assumption though. A mincemeat recipe found in a old cookbook contained 5lb of stewing beef - yum! Even modern mince pies are not necessarily vegetarian - mincemeat often contains shredded suet (the hard fat found around the kidneys of beef).
You can buy good quality mincemeat but in my experience it always tends to be cloyingly sweet. Making your own is easy and you can tailor the ingredients to suit your taste. I was never a fan of the mince pie before ...