We're Larfin?

It’s a favorite phrase of Jamie Oliver’s, and I figure it some sort of Cockney rhyming slang. He’ll say “just throw it in the oven for 40 minutes and you’re larfin.”

Working around the accent, I figure he’s probably saying his version of “laughing”, so the best I can reckon is, “laughing fool” = “cool”. It fits the context anyway, but I am just looking for confirmation or correction.

Maybe it is rhyming slang, but I’m not seeing the need for a rhyme, to go from “laughing” to “in a good situation”. It seems to me that the direct meanings of the words themselves aren’t implausibly far apart.

To my mind, it’s short for “you’re laughing all the way to the bank”. In other words, it’ll be a sure success.