Mix your ground flax-seed in water and set it aside to form flax egg.
Beat softened butter for a minute or so and add brown sugar to it. Beat this mixture till it turns very light and fluffy. About 2-3 minutes, using a hand mixer or balloon whisk.
Preheat your oven to 350 deg F and line a cookie sheet with silicon mat or parchment paper and set it aside.
Add both extracts and flax egg (strain if required) to the butter mixture. Mix well to combine.
Sift your flour, baking soda and cornstarch over this mix and fold just until flour disappears into the dough. Fold in the chocolate chips and chocolate chunks (if using) saving a few to press on top.
Form 5 cookie balls. About 3 tablespoons each. Roll them tall, about 2-2.5 inches in height.
Place mounts on your cookie sheet and stick the sheet in freezer until these mounts are firm to touch. About 5 minutes.
Bake the cookies for 13-15 minutes. They will still appear very soft in the center. But the cookies will continue to firm on cookie sheet as they cool. Don't over bake them.
Let them cool on the sheet for 5-7 minutes. While the cookies are cooling, you can press those saved chocolate chips and chunks on top of each cookie. Transfer on a wire rack to cool down further. Enjoy warm!