You can't visit Mocambo in Calcutta and not try the Prawn Cocktail.  Calcutta (not Kolkata!) = Mocambo. Even if it's been a fleeting visit, our pilgrimage to Mocambo is a must. In all the years that I've visited Mocambo, I cannot recall a single visit where we didn't order the Prawn Cocktail. Served in the icy…