In a large saucepan over medium heat, combine granulated sugar and water, stirring gently. Cook for about 10 minutes until sugar dissolves. It should begin bubbling and turning a rich amber color, which will take an additional 20 minutes.

Remove the caramel from heat and whisk in unsalted butter until melted. Gradually add heavy cream while whisking, then stir in vanilla extract and kosher salt. If needed, return to medium heat for a couple of minutes.

In a mixing bowl, combine old-fashioned oats, all-purpose flour, baking soda, and kosher salt. Whisk thoroughly to ensure no clumps remain.

In another bowl, cream together light brown sugar and unsalted butter until fluffy, about 2-3 minutes. Add eggs and vanilla extract, beating until smooth.

Gradually mix the dry ingredients into the wet mixture, folding gently with a spatula to combine without overmixing.

Line a 9x13-inch baking dish with parchment paper. Spread two-thirds of the cookie dough mixture evenly in the dish.

Sprinkle milk chocolate chips over the cookie dough layer, then drizzle the cooled caramel sauce over the chips.

Spoon dollops of the remaining cookie dough over the caramel layer, flattening gently while keeping some caramel visible.

Preheat oven to 350°F (175°C) and bake for 38-40 minutes until lightly browned. Check with a toothpick for doneness.

Once baked, allow to cool for 30 minutes, then chill in the refrigerator for 1 hour to set.