Using a medium-sized bowl, combine the flour, cornstarch, baking soda, and sea salt together. Set aside.

Using either an electric or a handheld mixer, cream together the butter and sugar.

While still mixing on low add in the egg and vanilla extract.
Slowly add the dry ingredients into the wet ingredients. Mix together.

Cover the bowl of cookie dough with plastic wrap and place in the refrigerator for 30-35 minutes.

Right before you remove the cookie dough from the refrigerator, preheat the oven to 350°F.

Line a baking sheet with parchment paper. Using your hands or an ice cream scooper, place the cookie dough on the baking sheet.

Bake for 9-10 minutes. Remove from the oven and let cool for 2 minutes on the baking sheet.