I hate to admit it, but I actually had to Google alfajores cookies.
The pictures that I saw reminded me of the Oreo cookies I ate when I was younger, but I suspect that they'd be a lot tastier, especially if I made them myself.
I think I'll go with your idea of condensing the milk first, and then I'll get my mom over to taste test it. It's been years since I've had sweetened condensed milk, and I don't remember the flavour since I was just a little girl the last time I had it. And now that I know about dulce de leche and alfajores cookies, I know what I'm going to be doing later this week...
Naomi