They're not techinically pudding, as they are stringy solids, like Noodles, but gross, but they are appealing to the critters that eat it so its fine. Its like ramen for Clangers that they MUST eat. Either that, or Green Soup.
There isn't really one, just take some blue vines and cook them over boiling water at 420°. But once, when the Clangers picked every last blue vine, they made artificial Blue String Pudding.
5 pounds of Ramen Noodles
½ a cup of milk
A jar of blue food colouring
A stick of butter
Boil it at 420° like normal, and serve.
Effect on Humans
Like how a Crumble Cracker turns one into a Fimble when comsumed, and Tubby Toast turns one into a Teletubby, this can turn one into a Clanger, other effecte are chestpains, overeating, loss of consciousness, and most commonly, going on a trip, this is earned via the fact that its cooked at 420°. Chuck Norris was the only human to try it, he teleported to the planet, tried some, and used his big brain to discover the effects on a puny morsel.
Early Clangers once lived on Earth, but the Italian Dinosaurs kicked them out, they went to a planet, and evolved via consumption of Primordial Mushrooms but started to starve, so they ate the blue strings raw, only for one took cook it over a geyser, and now there what they are to this day.
And then a meteor blew them up.