Suet

The solid, dense fat that encloses beef kidneys is true suet, and a substance very hard to obtain in its whole form as butchers no longer receive suet intact, with the kidneys in the middle.

Suet is the correct, traditional shortening for steamed puddings – sweet and savoury – and also always used to be used to make mincemeat: remember to make some adjustments if you are entertaining vegetarians.