Pour 2 cups wine and 2 cups water in a pot with the stock cube. Bring to a boil. Throw in the snails and when the liquid boils again, turn off the heat. Strain the stock and put aside. Melt the butter in a pan, add the snails and cook for a few minutes, then sprinkle with chopped parsley. Remove the snails again and discard the butter and deglaze the pan with the stock. Bring to a boil and reduce by half. Mix in the crÅme fraöche and maintain a boil until the sauce thickens. If you find the sauce is too thin, mix a teaspoon of cornstarch in a tablespoon water and whisk it in. Add the walnuts and snails to the sauce and heat without boiling. Serve hot.
