Combine flour, wheat germ, powdered milk in a large bowl. Cut in the butter until it resembles corn meal. Beat egg with a fork. Add mashed yams to the egg. Mix into dry ingredients and butter with hands until well mixed. Knead and roll out. Cut with cookie cutter. Bake at 325 degrees until lightly browned.
*If you can get rice or barley flour it is much better for your dog than whole wheat.