Preheat the oven to 350°F (180℃). Line a large baking sheet with parchment paper. Set aside.
Make the flax egg: In a small bowl, combine the ground flax seeds and water. Let it thicken as you prepare the rest of the recipe.
In a medium bowl, add the vegan butter, cane sugar and brown sugar. Beat together until creamy.
Add the vanilla extract and flax egg to the wet mixture and stir to combine.
In the same bowl, add the cornstarch, flour, baking soda and salt. Stir until combined. Avoid overmixing. You can use a different bowl for these dry ingredients before mixing them to the wet ingredients if preferred. Stir in the chocolate chips.
Roll the dough into 12 small balls and place them on the baking sheet, keeping some distance between each cookie.
Bake for 10-13 minutes or until lightly golden. Let them cool for 5 minutes, then transfer them to a cooling rack.