Salted Caramel Butter Bars

1 lb salted butter at room temperature
1 cup sugar
1 1/2 cups powdered sugar
2 tsp. vanilla
4 cups all purpose flour

For the filling:
1 bag (14 oz) caramel candies (about 50) unwrapped
1/3 cup milk or cream
1/2 tsp vanilla
1 Tbl coarse sea salt (optional)

To make the crust:
In a large bow, combine the butter and sugars. Using a mixer o medium speed, beat together until creamy. Add the vanilla and beat until combined. Sift the flour into the butter mixture and bea on low speed until a smooth soft dough forms.
Spray a 9 X 13 inch baking pan lightly with non-stick cooking spray. Press 1/3 of the dough evening into the pan to for a bottom crust. Bake approximately 20 minutes. Let cool for 15 - 20 minutes.

While bottom crust us baking and remaing dough is chilling, make the caramel filling. Place caramels in a microwave safe bowl. Add the cream/milk. Microwave on high for 1 minutes. Remove from the microwave and stir until smooth. If caramels are not completely melted, microwave on high for 30 second intervals, stirring after each interval until smooth.
Pour the caramel filling over the crust. If you are going to salt the caramel, sprinkle it on caramel layer now.

Remove the remaining chilled dough from refrigerator and crumble it evening over the caramel. 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. These are very rich, so cut them into 1" squares.