Heat the oil in a large saucepan and gently fry the onions, garlic and chilli flakes for about 10 minutes or until soft and golden.
Meanwhile peel the butternut squash , scrape out and discard the seeds and roughly dice the flesh.
Stir into the sauteed onions then cover and continue to cook, stirring occasionally, until the squash starts to soften.
Add the stock, herbs and Parmesan rind and simmer gently for 45 minutes or until the squash is meltingly soft. Discard the herbs and parmesan rind, scraping any gooey cheese into the soup.
Liquidise the soup, add the creme fraiche and season to taste. SErve piping hot scattered with the Parmesan cheese shavings.