Just Enough Chocolate Chip Cookie Cake

Preheat oven to 350°F and grease a 6 or 8-inch skillet. Melt butter, then mix in brown sugar and granulated sugar until combined. Add egg and vanilla and mix lightly. Add flour, salt, baking soda, and cornstarch. Mix until smooth, then fold in chocolate chips. Press dough into skillet and top with extra chocolate chips. Bake 25 minutes for 6-inch or 35 minutes for 8-inch, until edges are golden and center is gooey. Sprinkle with flaky salt and serve warm.