In a medium saucepan, melt ¼ cup of unsalted butter over medium heat. Stir in ⅓ cup of light brown sugar and whisk in ½ cup of heavy cream. Cook for about 5-7 minutes until thickened.

Remove from heat and mix in a generous pinch of flaky sea salt. Set the caramel aside to cool at room temperature.

In a large mixing bowl, whisk together 2 cups of all-purpose flour, 1 tablespoon of cornstarch, 1 teaspoon of baking soda, and ½ teaspoon of fine sea salt.

In another bowl, cream together ½ cup of unsalted butter with ½ cup of granulated sugar and ½ cup of light brown sugar until light and fluffy.

Add 1 large egg and 1 teaspoon of pure vanilla extract to the butter mixture. Mix until fully combined. Gradually blend in the dry ingredients.

Gently fold the cooled caramel into the dough until swirled. Do not fully incorporate.

Preheat oven to 350°F (175°C) and line a baking sheet with parchment paper. Scoop dough onto the sheet 2 inches apart. Bake for 10-12 minutes.

Sprinkle a pinch of flaky sea salt on top of each warm cookie. Cool for 5 minutes before transferring to a wire rack.