The best Millionaire Shortbread Recipe! Buttery shortbread, smooth caramel and a layer of chocolate come together to make the most delicious caramel shortbread recipe ever. A great bar to feed a crowd or include on your Christmas cookie tray!
Line a 9x13” baking pan with parchment paper and grease.
In the bowl of a standing mixer, or in a large bowl with a hand-held mixer, cream together the butter and sugar until light and fluffy (about 60 seconds).
Add egg yolk and vanilla and beat until combined.
Add flour and sea salt and beat until the mixture comes together into large crumbs.
Press the mixture into the prepared pan in an even layer and gently poke the top all over with a fork.
Bake in preheated oven for 20-25 minutes, until the sides are lightly golden brown.
Remove from the oven and set on a wire rack to cool while you make the caramel.
Make the caramel:
Put butter, brown sugar, corn syrup, condensed milk and sea salt in a 4-quart saucepan.
Cook over medium-low heat until the caramel reaches 225-235 degrees F on a thermometer, stirring frequently This takes about 30-40 minutes. Do not rush it.
You will know you’re getting close when the caramel becomes slightly darker brown in color (but it’s still light brown), thickens and pulls away from the sides of the saucepan as you stir. It will also remain solid when removed from the pot and left to cool or put in cold water.
When the caramel is finished cooking, remove from heat, add vanilla and stir vigorously.
Immediately pour over cooled shortbread.
Place bars in the refrigerator or outside on a cold day to cool and for the caramel to set. Chill for about 30-60 minutes.
Make the chocolate topping:
Once the caramel is firm, make the chocolate topping.
In a small saucepan, heat the heavy cream over medium heat until it just begins to bubbles around the edges, but does not boil.
Reduce heat to low, add chocolate chips and whisk until the mixture is smooth and glossy.
Remove from heat, add vanilla and whisk to combine.
Pour over firm caramel and let sit at room temperature or in the refrigerator until the chocolate is set (1-2 hours).
Cut into squares and serve at room temperature.
I don't recommend making any substitutions. However, here are a few possible ingredient swaps.
Salted Butter. I do not recommend making substitutions for salted butter.
White Sugar. Granulated white sugar is the best in this millionaire shortbread recipe - I have also used pure cane sugar.
Fine Sea salt. Regular table salt can be substituted, you may need to decrease the amount by half.
Light corn syrup. The only recommended substitutes for corn syrup (to be used in the caramel) are brown rice syrup and golden syrup (for my UK friends). Do not make any other substitutions or you will run the risk of your caramel setting up.
Heavy Cream. In the chocolate topping, heavy cream can be substituted with half and half.
Semi-sweet Chocolate. Use any form of chocolate - chips, chopped bars, discs, etc. I prefer semi-sweet or dark, but you can use any variety to suit your tastes.
How do you cut millionaire shortbread?
The best way to cut these millionaire bars is to run a very sharp knife under hot water, wipe dry and then cut. Repeat between each cut, cleaning and warming the knife each time to avoid any crumbs.
Store these millionaire bars in an airtight container at room temperature for 5-7 days. You can also store them in the refrigerator and they will last a little longer, but you would want to let them sit at room temperature to warm up a bit before serving.
If you'd like to freeze these millionaire bars, here's how:
Place cut bars on a large baking sheet - not touching.
Freeze for 1 hour, or until hardened.
Wrap individually with plastic wrap and place them in an airtight container.
Store in the freezer for up to 2 months.
To thaw: remove frozen millionaire bars from the freezer and let them sit at room temperature until softened enough to eat.
How to avoid the butter separating from the caramel
Sometimes, as you're cooking caramel, the butter begins to separate from the mixture. Here are some ways to avoid separation.
Use salted butter. Be sure to use salted butter because the salt helps stabilize the caramel!
Avoid extreme temperature changes. Don't turn the heat up high in order to cook the caramel faster.
Stir constantly. Please don't walk away - this caramel needs to be stirred often.
Melt butter & sugar together. Make sure the butter and sugar melt at the same time in the beginning of cooking. You can chop the butter into smaller pieces to ensure that happens.
Use a thick stockpot to avoid uneven heating.
How to fix caramel if the butter separates?
Here are some ways to fix separated caramel, as long as you have not removed it from the saucepan you should be able to save it in one of these two ways:
Beat it! My sister said her butter separated, but my brother in law removed it from the heat and beat it vigorously and it re-incorporated! Then, if it's not finished cooking gradually heat the mixture over low heat until it's finished.
Add hot water. You can try to add 1 to 2 TBS of extremely hot (boiling) water to the mixture and beat it vigorously to re-combine the ingredients.