we've cooked our dogs food for ages,
I usually use about a kilo of mince, a cup of rice, and any vegies that are going soft, but ready for compost!, (no onions, danger apparrantly) and a clove or two of garlic(good for skin and flea repellant -strange dogs can eat garlic but not onions , I know!), fry it up with a little oil, then add water, enough to provide moisture and congeal. Once cooked, divide into old marg/butter containers and freeze.
Before dogs were domesticated they ate all of what they killed, fur, stomach contents, hence they recieved a lot of roughage and grains/grasses/vegies.
As I said, we've done this for years, our dogs have the healthiest skin and coats, but best of all, their digestion is GREAT! When ever we use commercial food, phew eeee! bottom burps are nasty!