Lobster and Oyster Ragout

¼ cupful butter
¼ cupful flour
¾ cupful oyster liquor
¾ cupful cream
¾ teaspoonful salt
¼ teaspoonful pepper cayenne
few drops onion juice
1 pint oysters parboiled
¾ cupful lobster diced
1 tablespoonful chopped parsley

Make sauce of first eight ingredients in top of double boiler, add oysters, lobster dice, and parsley; serve hot.