Cover the mussels with a tea towel and refrigerate until it is time to add them to the dish. Heat the oil in a large pot (a wok will also work). Add the garlic, lemon grass, celery cubes and chilli. Toast everything for approx. 2 min., then add the fish sauce and wine and simmer for approx. 2 min. Now add the mussels, cover with a lid and steam the mussels for 3-4 min. Shake the saucepan constantly, just like when you make popcorn. Discard any mussels that are not open and remove the lemon grass. Add the cream, basil, chopped celery, salt and pepper. Season to taste and serve immediately, while the mussels are nice and hot. Serve the mussel soup with wholemeal bread if desired.