We supply our birds with homemade suet cakes. We used to purchase them but were never sure of the quality of the contents, so decided to produce our own. We buy suet from one of the local butcher shops and create a mix including the suet, peanut butter, mixed birdseed, and honey. Some time ago I built a mold that allows us to make up to 32 cakes at a time, in a size that fits the usual store bought suet cages. We usually mold them up in the garage but due to the cold weather brought our production indoors. Here's a couple pics showing the mold empty and after filling with the mix:
