1.Place mussels in a saucepan with 1/2 cup wine. Bring to a simmer, cover and cook over low heat until mussels open, about 5 minutes. Reserve 4 mussels in shells, shuck remainder, and strain and reserve broth.
2.In a small pot heat up fish stock.
3.Heat oil in a heavy shallow saucepan. Add shallots and ginger, and sauté over low heat until soft. Stir in rice and cook briefly. Add remaining wine. When wine has been absorbed by rice, add mussel liquid. Cook over medium-low heat until it is absorbed, then gradually add fish stock, 1/2 cup at a time, until rice is nearly al dente but still moist and creamy. Season with salt and pepper.
4.Stir in scallops and shrimp, and cook about 5 minutes, until seafood is cooked. Stir in shucked mussels, butter and green onions. Divide among 4 shallow soup plates, garnish each portion with a mussel in the shell, and serve.