Ask your butcher for fat trimmings or, if you’re trying a little home butchery, set aside the fat scraps.
The key to rendering animal fats is to cook them low and slow.
To begin, separate meat that may still be attached from the fat (and keep it aside for cooking later).
Cut the clean fat into cubes and place them in a deep pot on the stovetop to heat over a very gentle heat. Otherwise, lay them out on a baking tray and put them into an oven, preheated to 120°C.
Render the fat until it’s a clear liquid. It might also contain small, crispy brown bits (the unavoidable bits of meat that could not be trimmed). Be careful during the slow heating – if the meaty bits burn, they can ruin the rendered fat, so stir often.
Once the fat is rendered down to liquid form, strain it through a clean muslin cloth into glass jars and store in the fridge (where it can have a very long shelf life). When cooled, it will solidify. As soon as it’s spooned into a hot pan (three or four tablespoons are generally a good start), however, it will quickly become liquid.