We're Larfin?

Factual Questions
#1

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.

#2

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.

#3

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.