Mystery vendor explained

In the last post there was a photo and video of a street cart that was selling something unknown to me.  My friend, Diana, solved the mystery. 

"He is selling camote, which is a dish made from calabazas, yams and platanos maduros braised together in syrup.  It is served with cinnamon and condensed milk - very sweet and rich.  The charcoal fire maintains the head of steam for the whistle and keeps the camote warm.  The camote vendor is ubiquitous in Mexico, we have seen them in every part we have travelled to, except Guanajuato.  Too difficult to haul the cart up and down the steep alleys I guess."