1. Line an 8-inch square baking pan with heavy-duty aluminum foil, tucking it into corners and letting at least 1 inch overhang on all sides.
2. Combine sugar, Marshmallow Fluff, evaporated milk, butter, cinnamon, cardamom, cloves, ginger, cayenne and salt in a medium saucepan and cook over medium heat, stirring frequently, until mixture is smooth and comes to a boil. Let boil for 5 minutes, stirring constantly.
3. Remove saucepan from heat, add chocolate and stir until smooth. Transfer to baking pan and smooth with a spatula. Refrigerate until firm, about 2 hours.
4. Grasp overhanging foil on either side of pan and lift fudge onto a cutting board. Remove foil and cut fudge into small squares to yield 32 pieces. Refrigerate in an airtight container between layers of waxed paper for up to 1 week before serving.