A question about how a story is narrated is typically a question of narrative technique, style, and tone, so let's look at the Pardoner's narrative technique, style, and tone in his tale about the greedy Flemish young men in Chaucer's The Canterbury Tales.
The Pardoner chooses a roundabout form of narration when he is asked to tell his required tale. He actually starts with a sermon! He preaches against gluttony and drunkenness and oath-swearing, expanding upon his ideas with stories from the Bible and references to other authorities, even quoting Seneca, a Greek philosopher. We readers wonder if the Pardoner will ever actually get down to telling his story.
Eventually, he does, but his tone suggests that he is still preaching a sermon and using the story as one of his examples. He is quick to insert his own opinions into the story, calling the actions of the young men abominable and damnable, for instance. He refers to the characters as “the riouteres” and “the hasardoures” (hardly complementary terms), and he labels them as the proudest and worst people ever. The Pardoner cannot seem to keep himself out of his own tale, but this fits with his prideful, self-centered, abrasive personality.
The Pardoner, of course, is an old fraud. He never practices what he preaches. In fact, he tends to do the exact opposite, and we already know that when he tells his tale. This adds a strong sense of irony to the story. It is told by a person who makes moral judgments about the characters, judgments that he will not apply to himself.