I've hand carried Hokkaido Milk Pudding which is more like a flan texture via carry-on on a TPAC 8-9 hour flight. I wouldn't entirely advise this as Narita security had a sign which looked like a pudding cup with a big NO circle on it. I think mine went through as it was still fairly solid at security screening.

People fly with frozen kosher meals and that may be a good reference point What Do You Do For Kosher Food While Traveling? along with some cooler/thermal bag suggestions.