In small blender, combine thawed blackberries, blueberries and vanilla extract until slightly smooth. Set aside.

In bowl, combine gluten-free flour, cornstarch, baking soda and blue butterfly pea powder.

In separate bowl or stand mixer, incorporate sugar and butter until smooth. Add prepared flax egg, berry mixture and psyllium husk and mix well. Stir in flour mixture until dough-like consistency forms.

Fold in chocolate chunks and walnuts.

Refrigerate for about 20-30 minutes. (This will make the dough a little firmer and easier to work with.) Note: If you prefer not to wait, you can simply spoon drop the dough onto a parchment-lined cookie tray and bake.

Remove dough from refrigerator and preheat oven to 405 degrees F. Use hands to form dough into 3-oz. balls. Arrange on parchment-lined baking sheet. Use fork to firmly press down each dough ball. Sprinkle each dough ball with salt. Return to refrigerator until oven is fully preheated.

Bake until cookie tops are golden brown and slightly cracked, about 8-10 minutes.

Cool for at least 15 minutes before serving.