Such things only work if you have either a real iron casserole pot or one of those fancy French ones
We have one like this (Came from Ikea for about a tenner)

Or the fancy and very cheffy version by Le Creuset which will cost you x3 at least

OH and you have to season them .... by burning a little olive oil in it and never scour it or you need to re-season it.
PS Just Googled that Le Creuset iron pot ........ £107
