>Oreshki

Thank you; that makes sense (lived in Latvia for a year, and that's probably where/how I came across them). Also, the description that name finds, of a dulce de leche filling, fits perfectly for my (vague) memory!

I'm having a total tip-of-your-tongue moment. As in, I'm 100% sure I've had such cookies before, but I have zero idea where and when that could have been...