First start by mixing all the dry ingredients together in a medium bow. Start with the flour, the baking powder the corn starch and the salt and set aside.
Now, cream the butter and the sugar using a hand mixer or a paddle attachment in a stand mixer. Mix the sugar and butter mixture for 3-4 minutes. Add in the egg and the vanilla and beat just until combined.
Add the dry mixture to the wet mixture and mix until just combiner. Add in the chocolate chips and mix one last time.
Grab your plastic wrap and cut a large piece of it. Place the plastic wrap on the counter and scoop our the cookie dough on the plastic wrap. Form a 12" log, wrap the cookie dough with plastic wrap and tie the ends. Place the cookie dough in the freezer for 1-2 hours.
Once the cookie dough has chilled in the fridge, pull it out and preheat the oven to 350F. Using a sharp knife cut 20 slices and place them on a large parchment lined baking sheet.
Bake for 15-17 minutes, let the cookies cool for 5 minutes before transferring to a cooling wrack. Enjoy with a large cup of milk!