1 package (18-1/4 ounces) chocolate cake mix
1 package (16 ounces) miniature marshmallows
4 to 5 tablespoons water
1 package (2 pounds) confectioners' sugar
1/2 cup shortening
1 can (16 ounces) vanilla frosting
Blue, orange and green paste food coloring
Miniature peanut butter cups
Malted milk balls
Clear vanilla extract
Prepare and bake cake mix according to package directions for cupcakes; cool completely on wire racks.
In a large microwave-safe bowl, combine marshmallows and 2 tablespoons water. Microwave, uncovered, on high for 1-1/2 to 2 minutes or until melted, stirring every 30 seconds. Stir in three-fourths of the sugar; turn onto a work surface coated with 3 tablespoons shortening. Knead until smooth and pliable, gradually adding remaining sugar and shortening. If necessary, moisten with remaining water. Wrap fondant in plastic wrap to prevent it from drying out. To decorate, set aside 1/4 cup frosting. Tint remaining frosting blue; frost cupcakes.
Invert two peanut butter cups and stack, securing together with a small amount of reserved frosting. Top with a malted milk ball, attaching with frosting. Repeat, forming 24 stacks. On a work surface lightly sprinkled with confectioners' sugar, roll a 1-1/4-in. ball of fondant into a 4-in. circle; drape over a stack. For eyes and mouth, gently cut out shapes using pastry tips. Repeat for remaining ghosts.
For pumpkins, stems and tendrils:
Tint desired amount of fondant orange. Wrap fondant around malted milk balls; shape into pumpkins. Add imprint lines with a veining tool or toothpick.
For stems and tendrils, tint a small amount of fondant green. Shape into stems; attach to pumpkins using vanilla. For tendrils, roll out remaining green fondant; using a pizza cutter, cut into thin strips. Gently wrap strips around toothpicks; set aside to dry. (Tightly wrap any remaining fondant in plastic wrap and store in a resealable plastic bag for another use.)
To finish cupcakes:
Place a small amount of reserved frosting on top of each cupcake; top with a prepared ghost. Carefully remove tendrils from toothpicks and attach to pumpkins, using vanilla. Attach pumpkins to cupcakes as desired.