I think that I did make these, maybe four or five years ago and commented on it on the KAF Baking Circle. I used a recipe from a cookbook (Was it called Baked Elements?), which unfortunately is now packed. It was by two brothers who structured the book around four elements, one of which was Dulce de leche. It is put in these cookies like sandwich filling. I remember that it used a lot of cornstarch. I think this was before I started the What Did You Bake Thread, so I may not have notes on it.