Fany Gerson, who I believe is a food celebrity, has just published a new book "Mexican Ice Cream". It is quite an involved process. Anyways an interesting read and introduction:
http://www.huffingtonpost.com.mx/entry/mexican-ice-cream_us_595288c0e4b0da2c731edccc
Are there any traditional nieves in Chapala or Ajijic?