Heat 1 tablespoon of the olive oil in a large, heavy bottomed sauce pan over moderate heat, and add 1/2 the onions, salt and pepper. Saute briskly until slightly golden, about 8 to 10 minutes, and add the garlic. Cook and additional minute, then add the white wine and reduce to half. Add thyme, saffron, clam juice or fish stock, and tomato juice and bring to a boil, then reduce to a simmer and cook over low heat about 10 minutes. Strain and reserve.
Working in batches or in more than one pan, heat the remaining olive oil over high heat and add the remaining onion. Saute briefly, stirring occasionally, until onions are beginning to color, about 4 minutes. Add mussels to pan, keeping them in 1 layer, and saute 1 to 2 minutes, then add a proportionate amount of broth. Bring to a boil, reduce immediately to a simmer and cook, covered, for 3 to 5 minutes or until all the mussels are opened. Toss in parsley and serve on shallow soup plates with about a cup of broth per serving.
c.1997, M.S. Milliken & S. Feniger, all rights reserved