Hello Zack, I am from Kolkata, I've lived in Japan myself for several months! Other than street food, please definitely try traditional Bengali food in a restaurant(Oh Calcutta! or 6 Ballygunge Place etc). We are famous for our seafood, which Japanese people love, which isn't common in other parts of India. The thing you had in the earthen cup is called mitha dahi in Hindi, and mishti doi in Bengali. It's a traditional Bengali dessert.