Shuck oysters and reserve the liquor. Strain the oyster liquor, and add the liquor into a saucepan. Pick over the oyster, make sure there are no shell pieces refrigerate the oysters. Add the clam juice, water, and vegetables into the saucepan, and bring to a simmer. Cover the saucepan and cook until the vegetables are fork-tender. Pour this mixture into a blender and blend until smooth. Return this mixture back into the saucepan. Add the butter and flour stir with a whisk until combined and there are no lumps. Add the lemon juice, lemon zest, salt, pepper, egg yolks, whipping cream and sherry simmer for approximately 2 minutes or until everything is well blended. Add the oysters and continue to simmer until the oyster edges curl. Garnish with oyster crackers.