Cream the butter and sugars together until smooth and creamy. Beat in the eggs and vanilla extract. In a separate bowl, combine the 1 ¼ cups of flour, baking soda, and salt, then add this to the creamed mixture, mixing just until combined. Gently fold in the oats and white chocolate chips. Place the remaining 2 tablespoons of flour in a small bowl and lightly coat the blackberry pieces to prevent the batter from turning purple. (This step helps keep the batter from discoloring when the blackberries are added. For even less color bleed, you can freeze the blackberries for 30 minutes before coating them in flour, though it’s not necessary.) Carefully fold the blackberries into the dough, distributing them evenly but gently to avoid breaking them up. Using a cookie scoop, drop the dough onto a greased baking sheet. Bake at 325°F for about 12-13 minutes. Let the cookies cool on the baking sheet for 5-7 minutes before transferring them to a wire rack to cool completely. Enjoy!