Happened to find a line in`The Last Song of Dusk´ by Siddharth Shanghvi "She handed him a glass of chassh" which tells us that chassh is an Indian drink. May also be spelled `Chhachh´ and `Buttermilk´ is just another name for it. Many breads are made with buttermilk, and it is also used in creamy soups and sauces. Hope this helps!