Preheat oven to 375 degrees F (190 degrees C). Lightly grease cookie sheets.
Mix the shortening, peanut butter, white sugar, brown sugar and buttermilk until smooth and fully combined.
Add the flour, baking powder, baking soda and salt to the peanut butter mixture and mix until well blended.
Drop cookies 2 inches apart on lightly greased cookie sheet. Flatten with a fork that has been dipped in flour. Bake at 375 degrees F (190 degrees C) for 10 to 12 minutes.
