Step 1Combine the flour, sugar, baking soda, salt, shortening and one-half cup peanut butter. Mix together until it resembles coarse meal. Add the corn syrup and milk. Scrape the dough onto a sheet of plastic wrap and form into a long roll about 2 inches in diameter. Chill the dough until firm.
Step 2Heat the oven to 350 degrees.
Step 3Cut the dough into slices one-fourth inch thick. Place half of the dough slices about 2 inches apart on an ungreased baking sheet. Dab the center of each slice with one-half teaspoon of peanut butter. Top with another slice of dough. Seal the 2 slices with the prongs of a fork. Bake until light golden brown but still soft to the touch in the center, 12 minutes.