How do you say brownie in Hebrew?

There isn't a direct translation for "brownie" in Hebrew. You would need to describe it, perhaps using a phrase like:

* עוגיות שוקולד קטנות מרובעות (ugiot shokolad ktanot merub'ot) - meaning "small square chocolate cookies"

This is the most accurate and descriptive way to refer to brownies in Hebrew. You could also use עוגת שוקולד (ugat shokolad) - chocolate cake - but that's less precise.