In the bowl of a stand mixer, affixed with the paddle attachment, beat the butter on medium-high speed until creamy. Scrape down the sides of the bowl and add both sugars and the hot water to the butter. Mix until light and fluffy. Add the egg substitute and vanilla extract to the mixture and mix until combined. Slowly add the flour, cornstarch, baking soda and salt to the sugar mixture, and mix on low until barely combined.

Remove the bowl from the mixer and fold the chocolate chips into the dough by hand. Dump cookie dough out onto plastic wrap and wrap the dough completely. Place wrapped dough in a ziplock bag, and into in the refrigerator, for at least two hours or overnight.

Once your dough has cooled, preheat oven to 350-degrees. Line two baking sheets with a Silpat or parchment paper. Scoop small cookie dough balls onto prepared pan, leaving a few inches in between dough balls. Bake in 350-degree oven for 10-11 minutes, depending on your desired doneness.

Let cookies cool on the pan for several minutes before transferring to a wire rack to finish cooling.