In a small saucepan over medium heat, melt ¼ cup of unsalted butter. Stir in ⅓ cup of light brown sugar until dissolved and bubbling, about 2-3 minutes. Whisk in ½ cup of heavy cream, simmer for another 2-3 minutes until slightly thickened. Mix in ¼ teaspoon of flaky sea salt and let it cool slightly.

In a large mixing bowl, cream together ¾ cup of softened unsalted butter, ¾ cup of packed light brown sugar, and ¼ cup of granulated sugar until light and fluffy, about 2-3 minutes. Beat in one large room temperature egg and 1 teaspoon of pure vanilla extract until well incorporated.

In a separate bowl, whisk together 2 ¼ cups of all-purpose flour, 2 tablespoons of cornstarch, ½ teaspoon of baking soda, and ¼ teaspoon of fine sea salt. Gradually add this to your wet ingredients, mixing on low until just combined.

Gently fold the cooled salted caramel into the cookie dough using a spatula, creating a marbled effect without fully blending the caramel.

Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper. Drop rounded balls of dough onto the sheet, leaving space for spreading. Bake for 10-12 minutes until edges are golden but centers remain soft.

Once baked, remove cookies from the oven and let them cool on the sheet for about 5 minutes before transferring to a wire rack.