Position a rack in the center of the oven. Heat it to 250 degrees F.
Place Doggy Biscuits mix ingredients in a medium size bowl. Add 1 large egg, 1/2 cup shredded sharp Cheddar cheese, 1/4 cup grated Parmesan cheese, and 1/4 to 1/2 cup (or more) hot chicken broth, beef broth or very hot water. Make a dough that is very heavy, but not sticky. Add more flour or water, 1 teaspoon at a time if dough is too moist (use flour) or too dry (use hot water). Turn out dough onto a floured pastry cloth and knead 8 to 10 times until elastic. Let dough rest for 5 minutes.
Roll out dough 1/2 of an inch thick and cut with a dog-bone shaped cutter. Place cookies close together as they will not spread. Bake for 1 hour. Rotate the baking trays in the oven (turn tray around 180 degrees F), and bake them another half hour. Cool the cookies in the pan for 1 minute, then transfer to a wire cake rack to cool completely.