In a medium sized sauce pan, over medium heat mix the cream, marshmallows, sugar, salt & oil. Whisk gently until smooth and well combined. Stir in the chocolate & walnuts, remove from the heat. Stir until the chocolate is melted and the mixture is smooth. Pour the fudge into the lined cake pan and refrigerate for atleast 3 hours, until firm. Unmold the fudge from the pan, cut into squares. This fudge will keep in the refrigerator for up to 1 week but it does seem