The chef was asked to cook an American dinner for the celebrity guests - and he unveiled a "chicken hot dog", which included tomato sauce inside the meat, complete with edible napkins emblazoned with a picture of the actor's face.
But Ashton Kutcher was left suspicious when he noticed some curious crispy pieces on top of the sausage.
He asked, "What are these things on top? All of the things on this food looks like the things I fish with... Are we meant to eat the napkin with the dog?"
Heston Blumenthal told the baffled star they were fried onions, but as he chewed on his first mouthful he then revealed they were in fact "fried meal worms".
Ashton Kutcher then proceeded to try and spit out the food, before admitting, "That is good. Everything's better when it's fried."