Preheat the oven to 325° degrees F. Lightly grease a 9×13-inch baking dish with cooking spray and line with parchment paper.
In the bowl of a stand mixer, beat the room temperature butter, granulated sugar, and powdered sugar together on medium speed for about 2 minutes, until light and creamy. Add the vanilla and mix until combined.
Turn the mixer to low and add the flour, mixing just until a soft dough forms. Do not overmix. Press 2/3 of the dough evenly into the bottom of the prepared pan.
Wrap the remaining dough in plastic wrap and place it in the refrigerator to chill while the bottom crust bakes.
Bake the crust for about 22-26 minutes, or until the edges are just turning a light golden color. Let the crust cool for about 15 minutes.
While the crust is cooling, place the unwrapped caramels in a microwave-safe bowl, and add the cream. Microwave on high for 1 minute, then stir well. If the caramels are not completely melted, continue microwaving in 30-second intervals, stirring after each one, until the mixture is smooth. Stir in the vanilla until combined.
Pour the warm caramel evenly over the slightly cooled crust and spread with a spatula, if needed. (If you are using sea salt, sprinkle it lightly over the caramel layer now.)
Remove the remaining dough from the refrigerator and crumble it evenly over the top of the caramel. Leave a few small gaps so you can see it peeking through.
Return the pan to the oven and bake for 26–28 minutes, or until the caramel is bubbly around the edges and the top is set and lightly golden.
Let the bars cool completely in the pan on a wire rack.
Use the parchment to lift the bars out of the pan and place them on a cutting board to cut and serve.