Preheat oven to 350°F. Mix all dry ingredients in a medium bowl. In another bowl, cream butter, peanut butter, buttermilk and brown sugar until smooth. Add dry ingredients to wet ingredients; stir to combine. Add chocolate chips.
Roll cookies into 1 inch balls, place on a greased baking sheet. Flatten cookies with a fork.
Bake 8-10 minutes. Let cookies cool on trays 5 minutes, and then transfer to a cooling rack.