Preheat the oven to 350 degrees(F).
Now in a large mixing bowl, add the vegan butter and 1 cup of brown sugar. Using a hand mixer or stand mixer, whip together until light, fluffy and fully combined.
Then add the vanilla and continue to mix to combine. Set aside.
Next, in a separate mixing bowl, sift the flour and cornstarch. Then stir in the salt..
Start adding the dry ingredients to the butter/sugar mixture a little at a time. Continuing to mix with the mixer. Until everything is fully combined. It may seem crumbly as you do it, but it will be the perfect texture once you have mixed everything completely.
Now, taking a 13x9 inch pan, line it with parchment paper. Then take the dough and press it down evenly into the pan. It will be a pretty thin layer. I like to spray my hands with non-stick spray so the dough doesn't stick to my hands when I press it down. Then I use a cup to flatten it out.
Sprinkle the remaining brown sugar over the top of the dough evenly.
Bake for 25-30 minutes or until golden brown. The brown sugar on top won't really melt, it just crystalizes on top, creating a crunchy sugar topping.
Then, while the cookie base is still hot, sprinkle evenly with the chocolate chips. Let sit for 5-7 minutes or until the chocolate melts. Then spread the melted chocolate out evenly over the cookie base.
Next, sprinkle with the chopped nuts and a bit of salt.
Let cool completely, then cut into bars. They keep well in the fridge for about a week.