Clean the mussels thoroughly.
Add white wine, thyme, mussels to a wok and cover. Bring the mixture to a boil over high heat. Then reduce the heat to the medium level and cook for 10 minutes.
Discard any mussels that fail to open.
Using a slotted spoon, transfer mussels to a pot. Remove thyme and reserve the cooking liquid aside.
Peel sweet potatoes and cut them into small cubes.
Heat olive oil in the wok. Then, add yellow onion and fry until the onion is translucent.
Add sweet potatoes and curry powder to the wok, heat the mixture for about 2minutes.
Now add the cooking liquid of the mussels and vegetable stock to the wok. Cover the wok and cook for about 30 minutes.
Use a waffle-head potato masher to mash the sweet potatoes. Alternatively, use a hand mixer to mash the sweet potatoes.
Mix the cream with the mashed sweet potato.
Transfer the sweet potato into four large soup plates and add the cooked mussels.
Season with black pepper and salt. Optionally, spread some chopped fresh parsley.
Serve warm immediately.