In a large bowl, combine:
4 sticks (yes, 1 POUND) salted butter, at room temperature
1 cup white sugar
1 1/2 cups confectioners’ sugar
Using a hand-held mixer on medium speed, beat together until creamy. Add 2 tablespoons of vanilla and beat until combined.
Gradually add 4 cups of all-purpose flour to the butter mixture. Beat on low speed until a smooth soft dough forms.
Preheat your oven to 325 degrees F. Spray a 9×13 baking dish with cooking spray. Press one half of the dough evenly into the prepared pan to form a bottom crust, and place the remaining dough in the refrigerator.
Bake in the preheated oven until the edges are pale golden brown, about 20 minutes. Let cool for 15 minutes.
While the crust is cooling, make the caramel filling. In a microwave-safe bowl, combine:
One 14-oz. bag caramel candies, unwrapped
1/3 cup heavy whipping cream
1/2 teaspoon vanilla
Microwave on high for 1 minute. Remove from the microwave and stir until smooth. If the caramels are not completely melted, microwave for 30-second intervals, stirring after each interval, until smooth.
Pour the caramel filling over the crust. Sprinkle 1 tablespoon of coarse sea salt over the top.
Remove the remaining dough from the refrigerator and crumble it evenly over the caramel layer.
Return the pan to the oven and bake until the filling is bubbly and the crumbled shortbread topping is firm and lightly golden, about 25-30 minutes. Let cool before cutting into squares.
After your first bite, you will likely forget about all of that butter. I did.
Found this amazing recipe and photos from http://www.pipandebby.com/pip-ebby/2012/2/21/salted-caramel-butter-bars.html