Old or sick ferrets are often given "duck soup" to help them through their illness, gain weight, and survive. I have never heard of a recipe that actually contains duck.
The term duck soup simply means any ferret food converted into a soup, gravy, or gruel so the elderly have an easier time eating it. It is a good idea to give this special food to the younger, healthy ferrets once in a while so if they do get sick, they transition easier to soup. Most of my young ferrets think it is a special treat.
This is how I make duck soup for my kids.
I go to the grocery store and get a whole chicken. These are the chickens that have been de-feathered and have had their heads removed. Typically sold in plastic, the gizzard, heart, and neck are stored inside the body cavity.
Next, take the chicken out of the plastic. Pull the gizzard, heart, and neck out. Rinse everything and then put it in a big stockpot. Fill the pot with water and boil. And boil. And boil. Poke the chicken once in a while with some tongs and keep boiling until the meat easily falls off the bones.
Chickens have a lot of fat. Do not try to get rid of the fat. The ferrets like the fat and the soup mixes better in the end.
Once the chicken has been sufficiently cooked (at least a couple of hours), start removing the bones. I use tongs and pull them out one by one until they are all gone. I usually have my husband make a pass for bones too.
Turn the heat off.
Next, get out your stick blender and start blending the mixture right in the stockpot. You can transfer the mixture to a blender, but I do not recommend it. Every time I have tried to puree the bird in a blender, I have ended up with very hot chicken water on my face, and it hurt. Follow your stick blender's instructions. Mine, for instance, instructs to only pulse the blender for a maximum of 50 seconds at a time.
Once mixed and cooled, the puree is ready to serve to your ferret.
Take the extra soup and pour it into ice cube trays. Freeze. Once frozen, remove the chicken cubes from the trays and store in some kind of airtight container in the freezer.
Microwave a couple of cubes for about thirty seconds and stir to use the cubes.