In Britain, traditional mincemeat pies are actually single-serving little things, nothing like the 10-inch-diameter pies Americans make, Chowhound home cook lemons says; the small size ensures the proper ratio of crust to filling. Historically, the pies contained minced meat, but that's long since fallen out of fashion, Harters says. Nowadays mincemeat filling is mostly chopped dried fruit and beef kidney fat (i.e., suet). Harters used to make his own filling. Now he buys the best available at the supermarket and enhances it with a good slug of sweet sherry, and flavors his pastry with orange zest, sugar, and orange juice.
Suet is absolutely crucial for the special texture of mincemeat pies, Karl S says. Beef fat turns waxy when cold (think tallow candles), so mincemeat pie should always be served warm. One way to tell if a mincemeat pie contains real suet: if, when cold, it doesn't taste waxy.
Discuss: The Great British Mince Pie