Whisk together all the dry ingredients except for the chocolate. Cut the butter in, then add the peanut butter and work the mixture until it has a course meal texture. Stir in the milk and continue to work the dough, then fold in the chocolate chunks.
Shape into a long log shape 2" in diameter on plastic wrap. Seal and refrigerate to chill for 1 hour. The mixture will be dry but will hold together.
Remove from the refrigerator and slice about 1/4" thick placing on an ungreased cookie sheet.
Bake at 350F for 12 min. Cool on the cookie sheet for 5 min. then remove to a cooling rack.
Nutrition calculation is an estimation only. If you need nutritional calculations for medical reasons, please use a source that you trust.