I just made these bad boys (from the beautiful blog flagrante delícia), and I have to say that I feel sorry for my roommate, whose gluten- and dairy-free life prevents her from indulging in the decadence of thick creamy caramel just barely contained by flaky shortbread. Add chocolate and coconut on top, and I've now consumed the amount of calories I burned in my 90 minute run today...thank goodness I ran!
I've always been hesitant to make caramel by boiling a closed can of sweetened condensed milk for hours, since I feel like I should be able to make real caramel (see Dave Leb's post on how to make it just right) from good ole sugar and cream. However, for dulce de leche I decided to give this method a try, and I see the merit: it produces a wholly different consistency and flavor than could be produced through scratch caramel creation, and the process couldn't be simpler. I would recommend making the caramel a day or two prior to making the cookies, since it takes so long to be done (3.5 hours) and needs to cool completely before you work with it.
A couple of pointers on the alfajores: the crumbly dough will need to be worked into a ball by hand, and then should be rolled out as thin as possible; if it is thicker than 3-4 mm, the cookies will take longer than 5 minutes to bake. To produce the tenderest cookies possible, you'll want to remove them from the oven before they're browned on top. You'll know that they're done when they've puffed a bit taller (as in the photos, you can see some layers on the side of each cookie) and when you poke at them they feel dry to the touch and slide on the parchment paper. They end up very delicate, so dipping in chocolate is difficult unless you have the right equipment. You can always drizzle with chocolate instead!
If you don't have a kitchen scale, I've converted the gram measurements into American volume measures in parenthesis.
Alfajores con dulce de leche
Makes 40 (20 pairs):
Dulce de leche
1 can sweetened condensed milk
Place the can totally immersed in water in a pan.
Bring to boil over high heat.
Reduce to low heat and keep boiling for 3 1/2 hours.
Add water as needed.
Open the can when completely cold (very important!).
You can also use a pressure cooker.
112 g cornstarch (1 C)
125 g wheat flour (1 C)
50 g butter, softened (~ 1/2 stick)
62 g icing sugar (1/2 C)
2 g baking powder (1/2 tsp)
1 tsp vanilla extract
Pre-heat the oven to 250ºC.
Line a baking sheet with parchment paper.
In the bowl of an electric mixer fitted with the paddle attachment, cream together butter and sugar on medium speed until light and fluffy.
Add the egg and the vanilla extract and continue mixing until well combined.
Add the sifted flour with the cornstarch and baking powder and mix until smooth.
Roll out the dough (3-4mm thick) over a floured worksurface.
Cut 5 cm diameter cookies.
Place the alfajores into the prepared baking sheet.
Bake for 4-5 minutes.
Transfer cookies to a wire rack until completely cool.
Spread the bottoms of half of the cookies with a generous layer of dulche de leche.
Sandwich together with remaining cookies.
Coat with chocolate or grated coconut.