Preheat your oven to 350°F (175°C).
Line a 9x13 inch baking pan with parchment paper, leaving overhang for easy removal.
Cream together the salted butter, light brown sugar, and granulated sugar until light and fluffy.
Add in the eggs and vanilla extract. Beat until smooth.
In a separate bowl, whisk together the flour, baking soda, and Kosher salt. Gradually add to the wet mixture, mixing until just combined.
Fold in the semi-sweet chocolate chips gently.
Spread half of the cookie dough into the prepared baking pan.
Melt the caramels with the sweetened condensed milk in a microwave-safe bowl until smooth.
Pour the melted caramel mixture over the cookie dough layer.
Drop spoonfuls of the remaining cookie dough over the caramel layer.
Bake for 30-35 minutes until edges are golden brown and center is set.
Cool in the pan for 10 minutes, then sprinkle flaked sea salt on top.
Lift out using parchment paper, cool completely on a wire rack, and cut into squares.