I got my recipes from the gourmetsleuth site posted above. My favorite is the fish cookie because it gives Charlie extra Omega-3s. I also add ground flaxseed for the same reason.
Here is my "adjusted" fish cookie recipe:
I N G R E D I E N T S
1 14 oz can of salmon (or other fish - we tried mackerel recently)
1/4 cup dried parsely
2 cloves minced garlic
3 eggs including shells
1/2 cup ground flaxseed
2 cups (or more as needed) whole wheat flour
I N S T R U C T I O N S
Preheat oven to 375°F
Spray Cookie Sheet with cooking spray oil
Put all ingredients, except flour, into a mixer on medium till well combined. Add flour until blended and the mixture forms into a stiff dough using extra flour as needed.
Turn out dough onto a lightly floured work surface and kneed for about 1 minute. Roll out to a thickness of about 1/4". Cut into shapes using a cookie cutter dipped in flour. Place on greased cookie sheets. Bake treats for about 30 minutes or until firm and nicely browned. Cool treats on a wire rack.