Ghotab is one of three types of sweets ("shirini") that the Iranian city of Yazd is famous for producing. Yazd is an ancient city that was once a center for Zoroastrianism and is now famous for its architecture (along with the shirini!). The confectioners of Yazd keep their recipes very secret and many have been passed down through several generations. Other shirini famous in Yazd are baghlava and pashmak.
Ghotab is relatively easy to make, although my ghotab was not homemade by me, but purchased from Mashti Malone's, which is also an excellent source for Iranian-style ice cream in flavors such as rosewater saffron, orange blossom with pistachios and the intriguing "herbal snow," an ice cream containing 14 different herbs and spices.
Here is a simple ghotab recipe, although the measurements are metric, which is confusing for us yankees, but if you need a guide, this site has metric measurement conversions.