Misti dahi khave. Bengali sweets, and rasagolla are popular. I personally have a different choice when it comes to sweets. I love rasmallai more than anything else.
That shop looks like a very posh one. The rates must be higher. But as a metro city, Kolkata is lot cheaper than other metro cities.
Have you ever tasted cocoa based sweet? Try it if you find it in India. They are available. Taste is unique.
Will be on my hunt :)