Salty Twix Bars

Source: Une Gamine dans la Cuisine

Salty Twix Bars
from Bake and Shake

Crust ingredients:
1/2 cup (1 stick) of room temp. butter
1 1/4 cups of all purpose flour
1/2 teaspoon of kosher salt
2 Tablespoons of sugar

Dulce de leche ingredients:
1 (14 oz) can of sweetened condensed milk
1/2 cup (1 stick) Salted butter cut into cubes
3 Tablespoons of dark brown sugar
dash of kosher salt
1 teaspoon of vanilla extract

Chocolate topping ingredients:
6 ounces of chopped dark or bittersweet chocolate
1 Tablespoon of butter

Preheat the oven to 350F. Butter or spray an 8x8 inch square baking pan (bottom and sides.) Set aside.
Crust: In a medium bowl, beat the butter until it becomes light and fluffy, just a minute or so. On low speed, add the flour, salt and sugar and mix just until a crumbly dough forms. Try not to over mix. Press the dough into the prepared pan, going up the sides a bit. Prick the dough a few times with a fork. Bake for 15-18 minutes or until the crust is just starting to turn a light gold. Remove from the oven and cool completely. You may turn off the oven at this point since you won't need it again.
Dulce de leche: Empty the can of sweet milk into a heavy, medium sized pot. Add the cubed butter, brown sugar, and salt. Place the pot over medium-low heat and stir until the butter has melted. Turn the heat up a bit to a medium heat. Stir constantly until the mixture resembles a thick light golden caramel. Depending on how high the heat is, it may take up to 15 minutes. Be sure to keep stirring to prevent the bottom from burning. The longer you heat the mixture, the deeper the flavour till be. Once the mixture is thick and gold, remove from heat and quickly stir in the vanilla extract (be careful not to burn yourself as the caramel may sputter.)
Immediately pour the mixture over the cooled crust and spread it evenly before it hardens. It should be easy to spread as long as you don't hesitate too long. Set the bars aside to cool for about 20 minutes.
Chocolate topping: Place a heatproof bowl over a pot of simmering water. Make sure no steam is escaping from the pot. Place the chopped chocolate and butter into the bowl and stir until you have a smooth, shiny mixture. Carefully remove from heat and drizzle the chocolate over the cooled dulce de leche layer. Sprinkle some sea salt over the chocolate before it cools. Chill the bars completely before serving.
To cut the bars, run a sharp knife under hot water. Quickly and confidently, run the hot knife through the bars. Repeat as necessary.