This is a small lump of grey matter (not the stuff that’s in your head) formed together into a golf-ball sized, somewhat cylindrical form and surrounded by a layer of brittle pastry, and between the two, a transparent gelatine goo keeping the two together.
When you bite into the pie, the pastry falls away and you encounter the reconstituted mess of pork, lard and hydrogenated oil that form a lubricating layer on your bottom lip. Lovely.
If you must eat one, go for the fancy-pants posh homemade variety you buy from an old dear at a street food market in an upmarket area.
They don’t use the horrible gelatine goo. Which is in fact designed to keep the meat from going off. Which is quite telling. Encounter a pork pie at a petrol/gas station “fresh” food section might have been there for days, weeks even, in some cases months. You have been warned.