Puppy mush is the first solid food for most puppies. It's a gruel of dry dog food, that is easy to eat. This is fed as a supplement to the mother's milk, and gradually fed larger and more frequent meals until the puppies are weaned and no longer nurse.
Put a cup or two of dry dog food into a mixing bowl or pan. The amount is determined by the number of puppies and their size. This is the first time the puppies are eating solid food, and most of them will end up wearing more than they eat, so you only need enough so they all get a taste. It's best to use the same dry food their mother has been eating, which should be a high-quality puppy food while she's nursing.
Add an amount of puppy formula to cover the dry food. You can use plain water instead of puppy formula, but if the mother is no longer able to nurse the pups, formula is best.
Cover the bowl and allow it to stand long enough to get soft, about 15 to 30 minutes, depending on the amount of food.
Stir and mash the softened food until it is the consistency of a thin porridge. Add a little more water or formula if needed. As the puppies grow and learn to eat better, you can gradually thicken the mush, but keep it thin at first. You can add canned dog or puppy food at this point, but for the first meals keep the amount very small or the mush will be too thick.
Remove the mush and clean up the puppy pen once all puppies have had their fill. If it sits too long, it could spoil. If the puppies are walking and seem hungry, they can have mush when they are around 3 weeks old. All puppies go through the same developmental stages, but some litters or individual pups move a little faster. Start with three small meals of puppy mush a day, and increase to four. The consistency of the mush should get more and more solid until the pups can all eat plain dry food.
Puppies should remain with their mother until they are 7 weeks old. The mother will need more and more breaks from the puppies, and the pups will nurse less and less during weeks 4 through 7, but the mother should not be completely taken from them. Usually, the mother is the best judge of how much the puppies should nurse.