||Pour the white wine into a large pot and bring to a boil. Add mussels. Cover and cook over high heat, shaking the pot vigorously from time to time, for 4 minutes or until mussels open. Remove pot from heat and, using a slotted spoon, transfer mussels to a baking sheet to let them cool. Discard any mussels that are still closed.
When mussels have cooled enough to be handled, remove the meat from the shells over a bowl to reserve cooking liquid. Put mussels in the bowl with cooking liquid and place shells on baking sheet. Cover bowl of mussels with plastic wrap and set aside, or refrigerate if you plan to serve them at a later time.
||Halve the shells and set the most attractive ones aside for serving.
||Heat olive oil in a small frying pan over medium heat. Add mushrooms and garlic and sauté for 5 minutes or until mushrooms are tender. Drizzle with lemon juice and cream. Season with sea salt and black pepper to taste. Place mussel shells on a baking sheet. Place a cooked mussel in each shell. Spoon a dollop of mushroom garnish on top of each mussel. Serve warm or at room temperature.