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.
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.
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.
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.
