Millionaire Shortbread

In time for holiday cooking, "Cook's Illustrated Magazine" recently published a recipe that I tested and tasted last spring. I became acquainted with this cookie in 1977 during my first trip to Ireland where Leon served his LDS mission. Some of his favorite friends were the McKennas in Bangor, Northern Ireland. Molly McKenna served us a cookie called "Fudge Bars," chocolate and caramel on shortbread.  She shared a recipe with me but I didn't cook it since I couldn't find an ingredient:  Lyle's Golden Syrup (a sugar byproduct which is currently more available in the States). Ultimately, I lost her hand written recipe. The cookie was a favorite in my memory so I've been thrilled to know of a published recipe using ingredients easily found in U. S. supermarkets.

Making the caramel layer can be an adventure in candy making even though the magazine's instructions are pretty straightforward. If you live at higher altitudes, cooking the caramel becomes problematic. Since Betsy and I live at a slightly under 5000 feet, we can not successfully make this recipe as it is written. I am posting this recipe for those of us that live between 4000 to 5000 feet elevation but will tell you what to do if you live at lower or higher altitudes.

Do give this a try, even if you feel a little nervous. It's worth it and the recipe will be a great addition to your holiday repertoire.

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Millionaire Shortbread Bars (Irish Fudge Bars) High Altitude Version

Adapted from: Cook's Illustrated Magazine

Serves:  30-40 depending on how you cut them

Crust: 

2 1/2 c flour

1/2 granulated sugar

3/4 teas salt

16 T unsalted butter, melted

Filling:

1 (14-oz) can sweetened condensed milk

1 c packed brown sugar

1/2 heavy cream

1/2 c corn syrup 

8 T unsalted butter

Chocolate:

8 oz. bittersweet chocolate (6 oz. chopped, 2 oz. grated)

For the crust:  

Use foil to make a sling for a 9X13 pan: use two sheets folded to fit and laid perpendicular to each other, leaving the excess foil hanging over the edges of the pan. Make sure the foil is flush to the corners and flat against the bottom. 

Combine the flour, sugar, and salt and add melted butter. Stir well until all the flour is moistened. Spread the dough evenly across the bottom of the prepared pan. Press the dough with your hands or the bottom of a measuring cup until it is an even thickness. Pierce the dough with a fork at 1-inch intervals. Place in oven at lower-middle height and bake about 25-30 minutes until lightly golden and firm to the touch. Remove and place on a wire rack. Use a metal spatula to press on the surface of the crust while it is warm, making it easier to cut when cool. Let sit as it cools to just warm, 20 minutes at least.

For the filling (for different altitudes see below):

Mix all the ingredients together in a heavy bottomed, large saucepan. Over medium heat, cook while stirring frequently. Using a thermometer, either candy or instant-read, to test the temperature and cook until it reaches 226-229F (at 5000 feet elevation). When the caramel layer reaches your target temperature, carefully pour it over the crust and using a rubber spatula or an offset spatula, spread it to an even thickness. This mixture is very hot and could burn badly if it lands on you. Let the bars cool completely, at least 1 1/2 hours.

For the chocolate top:

Place the chopped chocolate in a small glass bowl and microwave at 50 percent power for 1 to 2 minutes, stirring every 15 seconds. The chocolate should be melted but not much warmer than body temperature. Stir in the grated chocolate and keep stirring until smooth. If it doesn't melt, you can return it to the microwave for 5 seconds at a time to finish. Stir well and spread the chocolate over the caramel layer. Place in the refrigerator for about 10 minutes until the chocolate is solidified but just barely.

Use the foil sling to lift the shortbread out of the pan. Place on a cutting board, removing the foil. Use a serrated knife to cut. I cut mine into squares. Cook's Illustrated cuts theirs into long, thin strips. 

The cookies can be stored at room temperature for up to a week. It is wise to use parchment in between any layers in your storage container.

Caramel Layer at Varying Altitudes

The only change required for this recipe is the target temperature for cooking the caramel. The original recipe calls for cooking the caramel layer to 236-239F

Atmospheric pressure is lower at higher elevations and it affects baking and candy making. If we ignore this difference our efforts will be disappointing. In this recipe the caramel will be too moist or too chewy if you cook it to the wrong temperature. Since boiling takes place at a lower temperature at high altitudes the target temperature must be lower too. But knowing just what temperature can be difficult. 

Several years ago Betsy and I attended a high altitude cooking class taught by Romina Rasmussen, chef and owner of Les Madeleines Patisserie and Cafe in Salt Lake City, one of the most helpful classes I've ever attended. Romina is a trustworthy resource so I spoke with her last summer and she told me that even a couple of degrees off in caramel making can make for an undesirable end result. She recommends boiling water the very day you are going to cook the caramel (apparently atmospheric conditions can affect candy, too). Test the temperature at which the water boils and subtract that amount from sea level boiling point, 212F. Then subtract the difference from the original recipe and you will have your target temperature.  Here's an example:

Sea level boiling point:  212F

Subtract your boiling temperature:  ___________ (at my 5000 ft it is 202F)

Equals:________ (10 degrees for me)

Original recipe target temperature:  236F-239F

Subtract the difference between two boiling temps:  _________ (10 degrees)

Equals: your target temperature (for me it is 226F-229F)