-(about 3 ounces) Butter an 20 cm-square baking pan. Line the bottom of the pan with foil. In a large bowl, combine the butter, chocolate chips, macadamia nuts, unsweetened chocolate, and vanilla. Attach a candy thermometer to a medium saucepan. Add the sugar, evaporated milk, and marshmallows. Bring to a boil over medium heat, stirring constantly to prevent burning. Cook, stirring constantly, until the mixture reaches 238 degrees. Pour the hot mixture into the bowl and let stand for 30 minutes. Stir until the mixture begins to thicken, about 1 minute. Spread evenly in the prepared pan. Let stand until completely cooled. Cover with foil and let stand overnight to allow the flavors to mellow. Invert the fudge and remove the foil. Reinvert and cut into squares. Store the fudge at room temperature in an airtight container. Makes about 2 pounds.