In your stand mixer fitted with the paddle attachment, beat together the butter, cream cheese, brown sugar, granulated sugar and vanilla extract on medium-high speed until the mixture is light and fluffy, about 3-4 minutes. Stop to scrape down the sides of the bowl as necessary. Add the egg and beat until well combined.

In a medium bowl, whisk together the flour, cornstarch, baking soda, salt and thyme. Gradually add the dry ingredients to your mixer, beating on low speed until no more white streaks remain. Fold in the chocolate chips. Cover and refrigerate the cookie dough for at least two hours or up to overnight.

Pre-heat your oven to 350 degrees. Line your baking sheets with parchment paper.

Scoop and roll the chilled dough into balls, using about 1 ½ tablespoon of cookie dough per ball. Then place the dough balls about 2-inches apart on your parchment paper-lined baking sheets.

Transfer the baking sheets to your pre-heated oven and bake the cookies for 8-9 minutes. Remove the baking sheets from your oven and sprinkle the tops of each cookie with a pinch of flaky sea salt. Then return the baking sheets to your oven and continue baking the cookies for an additional 2-3 minutes. The cookies should be puffed and just set around the edges.

Remove the baking sheets from your oven and allow the cookies to cool on their baking sheets for 5 minutes. Then transfer them to a wire rack to continue cooling.

Cookies can be stored in an airtight container at room temperature for up to 5-7 days.