While peanut butter cookie dough tends to be on the dryer side, as they cookie dough balls typically need to be pressed down with a fork creating the classic peanut butter cookie look. However, if the dough is too dry and you are unable to form a ball with it, most likely you did not add enough fat or liquid. For this recipe, try adding an extra teaspoon of milk and mix again. Continue adding 1 teaspoon at a time until you reach your desired consistency.