In a large bowl, cream peanut butter and brown sugar until crumbly; stir in flour. Cut in butter until mixture resembles coarse crumbs. Set aside 1/3 cup for topping.
In a small bowl, whisk the egg, milk and vanilla. Add baking powder and baking soda to the remaining peanut butter mixture; stir in milk mixture just until moistened.
Transfer to four 6-oz. ramekins coated with cooking spray. Sprinkle with reserved topping and chocolate chips. Bake at 350° for 30-35 minutes or until a toothpick inserted in the center comes out clean. Cool for 10 minutes before removing from ramekins to a wire rack to cool completely.