Use a little butter to grease a 13 x 9 serving dish
In a large pot combine the butter, evaporated milk, sugar, cinnamon, and cayenne pepper.
Cook over high heat, stirring continuously until the mixture reaches 234 degrees (use a candy thermometer to keep track of the temperature).
Remove from heat.
Stir in dark chocolate pieces until they are completely melted and completely mixed in.
Stir in marshmallow cream until it is completely mixed with the chocolate.
Pour fudge into a greased 12 x 9 serving dish (or Christmas tins) and let it set.