Chop the shallot, garlic, celery and sauté in little butter without browning, remove the shell from the half shell mussels and roughly chop. Add both shell on and chopped mussels to the sauté pan and cover for 2 minutes. Uncover the pan and remove the shell on mussels. Add saffron toss then pour in the wine, stock and reduce by half. Once reduced add the cream, salted butter and simmer for a few more minutes, toss in the al dente pasta and toss on low heat for a few minutes. Add the mussels shell on again, parsley, toss well and serve.