Line an 8x8 inch pan with aluminum foil. Set aside. In a large saucepan over medium heat, combine marshmallow cream, sugar, evaporated milk, butter and salt. Bring to a full boil, and cook for 5 minutes, stirring constantly.
Remove from heat and pour in semisweet chocolate chips and milk chocolate chips. Stir until chocolate is melted and mixture is smooth. Stir in nuts and vanilla. Pour into prepared pan.