In a medium saucepan, stir together the water, sugar, and corn syrup.
1 cup granulated sugar, ¼ cup water, 3 tablespoons light corn syrup
Heat over medium until it begins to boil. Once boiling, do not stir to avoid crystallization.
Continue boiling until the mixture turns golden brown. Be cautious as it can burn quickly.
¾ cup heavy cream
Meanwhile, microwave the heavy cream for 1 minute to warm it.
Once the caramel reaches a golden color, remove from heat and slowly add the warm cream while whisking constantly.
Stir in the vanilla extract, salt, and butter until fully combined.
2 teaspoons pure vanilla extract, 1 teaspoon salt, 1 tablespoon unsalted butter added to the caramel at the end
Transfer the caramel to a bowl and let it cool.
Make the Cookies:
Preheat your oven to 350°F. Line two baking sheets with parchment paper. Set aside
In a medium saucepan, melt the butter over medium heat. Continue cooking, swirling the pan occasionally, until the butter foams and turns a rich amber color with a nutty aroma, about 5-7 minutes.
8 tablespoons unsalted butter
Immediately transfer the butter to a large heatproof bowl and let it cool for about 15 minutes.
Once cooled, whisk together the brown butter, dark brown sugar, and white sugar for 30-45 seconds until well combined.
½ cup dark brown sugar packed, ½ cup white sugar
Add the whole egg, whisk until evenly combined, then add the egg yolk and whisk again. Stir in the vanilla extract.
1 egg, 1 egg yolk, 1 teaspoon vanilla
Add the flour, baking soda, baking powder, cornstarch, salt, and chocolate chips. Switch to a rubber spatula and gently fold until no streaks of flour remain. Do not overmix.
1 teaspoon baking soda, ¼ teaspoon baking powder, ½ teaspoon cornstarch, 1 teaspoon salt, 1 ½ cups all purpose flour spooned and leveled, 2 ½ cups semi sweet chocolate
Using a 3-tablespoon-sized cookie scoop, roll the dough into balls and place them on the prepared baking sheet about 2 inches apart.
Bake for 9-11 minutes, until the edges are golden brown and the centers are slightly soft.
If the cookies are thick, use the flat bottom of a cup to gently press them down so they are even on top.
Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
If desired, sprinkle flaky salt on top immediately after baking.
Optional: Flakey salt
Make the Buttercream:
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and cream cheese on medium speed for about 2 minutes until creamy and smooth.
4 ounces cream cheese softened, ½ cup unsalted butter softened
Scrape down the sides of the bowl and beat for another 2 minutes.
2 ½ cups powdered sugar, 1 teaspoon pure vanilla extract
With the mixer on low speed, gradually add the powdered sugar. Once combined, add the vanilla extract and a pinch of salt.
Increase the speed to medium and beat for 3-5 minutes until smooth and fluffy.
Assemble the Cookie Sandwiches:
Make sure the cookies are completely cooled before assembling.
Pipe a thick rim of vanilla bean buttercream around the edge of half of the cookies to create a well for the caramel. The rim should be sturdy but not overly thick.
Fill the frosting well with the prepared caramel sauce, being careful not to overfill.
Top each filled cookie with an unfrosted cookie, pressing gently to create a sandwich.
Serve and enjoy! Store any leftovers in an airtight container at room temperature for up to 3 days or in the fridge for up to a week.