Sizzles are the result of crossing a Frizzled Cochin and a Silkie.
Once the original cross is made they are then bred back to other Sizzles to hopefully develop a true breed. As with any Frizzle breeding you only breed Smooth birds to Frizzled birds with 50% of the offspring being Frizzled. To breed Frizzle to Frizzle you will get 100% frizzled birds but many of them will have organ problems as well as brittle and sparse feathering. It is possible to get both frizzled Silkies and Sizzles ( which is for all intents and purposed a Silkie with regular hard feathers)
My Sizzles are now 4th generation. They are not a recognized breed but may well get there, much like the showgirls. It takes many years to develop a new breed and lots of dedicated people who continue to work on a standard or perfection.