These cookies turn out every time and are delicious. My grandmother made them for me as a child and I have made them for years for my children. If I am ever low on shortening, I top the amount up with butter or a good margarine and it seems to make no difference.
I usually double it.
1 cup shortening, 1 cup white sugar, 1 cup brown sugar, 2 eggs,1 cup PB. Mix well. Then add 2& 2/3 cups flour, pinch salt, 1tsp. baking powder, 2 tsps. Baking soda. Blend well, form in balls, press with fork. Bake 350f, 10-12 minutes until golden brown. I use a glass lasagna pan lined with parchment paper, no dark bottoms.