Cream the shortening, peanut butter, white sugar, brown sugar and vanilla together, and blend for 3 minutes. Next add in the eggs one at a time, beating well after each addition. Then, sift the baking soda, flour and salt together, adding the flour mixture to the peanut butter mixture. Mix until combined, then stir in the chopped nuts.Cover and chill dough for 2 hours. Preheat oven to 350 degrees F . Pinch off 1 inch balls of the dough and place on a non greased baking sheet. Press tops with floured fork tines. Bake at 350 degrees F for 10 to 12 minutes or until edges are golden but the center is still soft. Allow to cool for 2 minutes on the sheet then remove to a rack to continue cooling.