syut gōu noh máih chìh
Mochi ice cream is Japanese mochi filled with ice cream encased. So it's not dim sum, but it's a popular dessert, and I've seen it on dim sum menus.
Mochi ice cream is actually a Japanese-American creation, invented by Frances Hashimoto of Mikawaya, a family-run Japanese confectionary based in Los Angeles. Her parents had to close the business during World War II when they were sent to an internment camp, where Frances was born, but after the war they restarted the business and eventually Frances took over the company and made mochi history.