Cooked food is a great option but you will need to discuss things with a vet or a nutritionist who can help you make sure it is balanced properly. An improperly fed diet whether kibble, homecooked or raw, can cause serious imbalances and thus serious health issues.
As viviansnickers said, raw is a great option for Yorkies who are picky. We ourselves feed prey model which means like Viv said, we buy our meat from the grocery store/butcher (or we order from meat processing companies) and balance our food ourselves. I will point out that PMR feeders do
not have to supplement if feeding correctly. We also do not feed any veggies or grains. Just 100% protein!
Good luck with whatever you decide. I know it can be tough.