Millionaire's bars, or millionaire's shortbread as some may know it, is much like an elevated, thick Twix candy bar. Share if you dare because these bars are always the first to go on the dessert table.
Preheat the oven to 350°F. Line an 8x8 or 9x9 baking dish with parchment paper and set it aside. Allow the parchment paper to slightly hand off the sides to make it easier to remove the bars from the pan.
In a large mixing bowl, beat the butter until light and fluffy using a hand mixer.
Add the granulated and brown sugar and beat until creamed together well. Beat in vanilla extract.
Add cake flour and salt and mix just until combined.
Use a greased spatula or fingers to pat the shortbread mixture into the prepared baking dish.
Bake for 30-35 minutes until shortbread is golden brown around the edges and set in the center. Cool.
Make the Caramel
Meanwhile, prepare the caramel by placing all ingredients in a saucepan over medium heat.
Whisk constantly until the mixture is fully melted and comes to a boil (do not increase the temperature.)*Be sure to stir the caramel constantly and keep the heat at or just below medium so that the caramel doesn’t burn on the bottom of the pan.
Fit the saucepan with a candy thermometer and continue whisking and cooking until the caramel reaches the soft ball stage, 225°F. This process can take 20-30 minutes.
Remove the caramel from the heat and pour over the baked shortbread, spreading it smooth to the edges.
Chill for at least 30 minutes to firm up the caramel so that it does not displace when the ganache is added.
Make the Ganache
To make the ganache, combine the chocolate chips and heavy cream in a microwave-safe bowl. Heat in 30-second intervals, stirring/whisking between intervals until the chocolate melts and the ganache comes together in a thick, smooth mixture.
Spread the ganache over the caramel. Sprinkle flakey sea salt over the top of the ganache and place in the refrigerator to chill for at least 30 minutes or until the ganache is set.
Lift the dessert from the pan and cut into bars with a sharp knife.
Notes
We used unsalted butter, but salted butter will work just fine in this recipe.
The shortbread is not a traditional shortbread that is made from just flour, butter, and sugar. Our version creams the butter and sugars together (and we added brown sugar) for a bit of a chewier base. While a traditional shortbread is typically crisp and buttery, this shortbread is buttery and flakey, but it is a bit softer and is easier to cut into bars and bite into.
Using an 8x8 pan or even a 9x9 pan will produce nice, thick bars. You can also spread the recipe into a 9x13 pan. The cook time of the shortbread will be a little shorter. The finished bars will be less thick, but still delicious.
Because these bars are so rich, you can definitely get away with cutting them into smaller portions.