Millionaire’s Caramel Shortbread or Homemade Twix

Another recipe from America’s Test Kitchen’s “100 Techniques” book , which is now definitely on my list of favorite cookbooks.

Shortbread is a cookie native to Scotland. It is made with sugar, flour and butter, with no added baking soda or baking powder. Shortbread gets its name because of its crumbly texture. The word “shortbread” used to have another meaning: “inelastic”.

Millionaire’s Shortbread is a Scottish shortbread with caramel filling and chocolate topping. This dessert has many different names, depending on the region. It is called: caramel shortbread, caramel slice, caramel square or millionaire’s slice. But the most popular and most familiar name to everyone would of course be “Twix”.

For simplicity, you can call this dessert a “homemade Twix”. Everything is the same here: a sandy base, caramel filling, and a top layer of chocolate.

Only we will use dark, bittersweet chocolate, but you can always replace it with milk one if you want.

⏱ Cooking time — 3 hours and 20 minutes overall. Includes 45 minutes of preparation and cooking + 2 hours and 35 minutes unattended.

🥣 Ingredients

🍽 For ~40 cookies:

For shortbread:

• 355 g (12,5 oz) of all-purpose flour
• 100 g (3,5 oz) sugar
• 3/4 tsp. salt
• 230 g (8 oz) unsalted butter

For the caramel filling:

• 400 g (14 oz / 1 can) sweetened condensed milk
• 200 g (7 oz) sugar (the original recipe calls for brown sugar, but I do not see the reason for that in this case)
• 120 g (4,2 oz) heavy cream
• 120 g (4,2 oz) corn syrup (or 120 g (4,2 oz) sugar + 30 ml (2 tbsp.) water + lemon juice from 1/4 lemon, I will tell you more about how to substitute the corn syrup in the recipe)
• 120 g (4,2 oz) unsalted butter
• 1/2 tsp. salt

For the chocolate layer:

• 225 g (8 oz) 50-60% dark chocolate

 🔪Step by step Directions

Prepare the batter

Preheat the oven to 180 °C (350 °F).

Melt 230 g (8,1 oz) of butter in a saucepan over a low heat.

Mix 355 g (12,5 oz) of all-purpose flour, 100 g (3,5 oz) of sugar, 3/4 tsp. salt and stir. Pour in 230 g (8 oz) of unsalted butter and knead the dough. Knead until there are no dry parts. Set aside.

Take a 33 cm by 23 cm (13 x 9 inches) baking pan, tear off two sheets of foil, one 33 cm long, the other 23 cm long. Place them perpendicular to each other in the pan. Press the foil into the corners. Do not tear the foil hanging off the sides – it will help get the cookies out of the pan.

Transfer the dough to the baking pan and spread it all over with your hands. Press down and tamp down to the same thickness. Prick the dough with a fork all over the surface.

Bake until golden, about 25-30 minutes.

Remove mold with dough from oven and use a metal spatula (or just a spoon) to press hot dough slightly over entire surface. Cool for at least 20 minutes.

Prepare the filling

After 20 minutes, prepare the caramel filling.

Substitute for the corn syrup

First of all, let’s deal with the corn syrup. I didn’t have any, so I replaced it with invert syrup.

To make it, mix 120 g (4,2 oz) of sugar and 30 ml (2 tbsp.) of water in a saucepan. You may now put it on a fire. Whilst stirring, allow the sugar to completely dissolve in the water and turn into syrup.

When it boils, pour the juice of 1/4 of a lemon through a fine sieve to prevent pips and other lemon parts from getting into the syrup. Stir, the syrup is ready.

Caramel filling

In a heavy bottomed (this is important!!!) saucepan or pot mix together 400 g (14 oz / 1 can) sweetened condensed milk, 200 g (7 oz) sugar, 120 g (4,2 oz) heavy cream, 120 g (4,2 oz) corn syrup (or an alternative we made), 120 g (4,2 oz) unsalted butter and 1/2 tsp. salt.

Place the saucepan over medium heat. Stirring frequently, bring mixture to 113-115 °C (235-240 °F) until light brown, caramelized, and thickened. This will take you 16 to 20 minutes. If you don’t have a thermometer – no problem, be guided by color and cooking time.

When the desired temperature is reached – remove from the heat and stir for another couple of minutes. Pour the mass into a baking pan with a shortbread base. Tilting the pan, spread the filling until equally thick.

Leave to cool for 1.5 hours.

Chocolate toping

Create a water bath: pour about 200 ml (0,8 cup) of water into a saucepan or pot and place a metal or glass bowl on top. Turn on the heat.

Break 225 g (8 oz) of 50-60% dark chocolate into the bowl. Cook constantly stirring until about half of the chocolate has melted. Turn off the heat.

While continuing to stir, melt the remaining chocolate. Pour the chocolate into the baking pan, spreading evenly. Place in refrigerator for 20-30 minutes or until chocolate layer is completely set.

Take the mold out of the refrigerator, remove the foil. Cut the dessert in half on the long side. Then cut perpendicularly into 15 to 20 equal pieces. Or divide into 4 long pieces and cut perpendicularly into 10 pieces.

Store in the refrigerator in the mold in which the shortbread was made, covered with clingfilm or at room temperature wrapped in parchment paper for up to 1 week.