I made it a few years ago. Tallow is trendy (and thus expensive), but you make it by rendering suet which is basically a throw-away product at butcher shops. Lots don't even bother selling suet, which is a pain. Rendering was just slow-cooking and removing the little pieces, then you're left with candle wax you can cook with.

I thought the candle wax consistency was a coincidence, but it was the main way to make candles for most of history. It tastes pretty good but has a strong smell when cooking (or burning as a candle, presumably).