The brownie was good enough for me to try to replicate it. I found this recipe on David Lebovitz's site and made the dulce de leche by simmering a can of condensed milk for about an hour and a half. Make sure the whole can is immersed in water otherwise you'll have a dulce de leche ceiling, floor, cabinets, etc...you get the picture.
The recipe produces a moist and dense brownie. The Buenos Aires brownie is a little lighter and drier and used almonds (I added walnuts). I would say it is a good first try, but I will have to bake a few more to replicate the Zingerman brownie.
If you do not want to bake them yourself then you can place an order for the Buenos Aires brownie using product code "a-bue".