In a medium saucepan over medium heat, melt the unsalted butter, then add the light brown sugar. Whisk in heavy cream until the mixture thickens and bubbles gently, about 5-7 minutes. Stir in a pinch of flaky sea salt and let cool slightly.

In a large mixing bowl, whisk together all-purpose flour, cornstarch, baking soda, and fine sea salt. Set aside.

In a separate large bowl, beat together unsalted butter, light brown sugar, and granulated sugar until light and fluffy, about 3-4 minutes.

Add the large egg and vanilla extract to the creamed butter mixture, mixing on low speed until just incorporated.

Gradually add the dry ingredients to the wet mixture, mixing on low speed until just combined. Gently fold in the warm salted caramel sauce.

Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper. Drop generous spoonfuls of dough onto the sheet, spacing them about 2 inches apart. Bake for 12-14 minutes, or until edges are golden.

Sprinkle warm cookies with flaky sea salt. Allow to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.