Story about girl who gets captured by giant and saved by man is recounted by a dwarf to an author

So I kind of have a rough idea of how the story goes, its like the girl is abducted by a giant (I don’t really remember the reason why she was abducted) and is kept in a cage and she is looked after well by two female monsters.
Finally the guy who loves the girl puts something in the monsters’ food and they all fall asleep. Utilizing this opportunity the girl and the guy run away and they are chased by the giant who returns home to find the girl missing. The girl and the guy are supposed to cross the river to get rid of the giant. The giant stamps so hard on the bank that the boat in which the guy and girl travel is overturned and the girl drowns and the guy searches for her in the river but she is nowhere to be found. The guy waits for the girl at the bank of the river and finally turns into a willow tree.
This story is narrated by a dwarf to the story teller. The storyteller sits by the window to write a novel and the dwarf pops out of nowhere and says that he would narrate the story and the story teller should type it but the storyteller dies without completing the story so the dwarf types the rest of the story.

What is the name of this story