Place the mussels in an ovenproof casserole or Dutch oven and cover. Cook over a high heat until they open, 3-5 minutes, shaking occasionally. Drain the mussels, reserving any liquid they exude. Heat the olive oil in the Dutch oven and add all of the vegetables and the parsley. Cook for 5 minutes, stirring occasionally. Sprinkle with the flour and cook for 3-4 minutes, stirring. Stir in 5 cups of water, half the lemon juice, reserved mussel liquid, and white wine. Season with salt and pepper. Simmer for 15 minutes. Add the mussels and return to a boil. In a small bowl whisk together the egg yolks, crÅme fraöche, and remaining lemon juice. Stir yolk mixture into soup and simmer for 5 minutes. Serve immediately.
