Apart Scarfo and the K&A gang in philly in the 80s, there are other cases of families that are very involved in the methamphetamine traffic.
In theory, if you can cook the cookies, you can cook the meth, it's also most powerful and most cheap of cocaine or heroin, and can also be produced in a craft workshop in the basement.
Also having the Mafia unsuspected knowledge, could easily obtain ephedrine and other chemical components that are used to prepare the meth.