1. Cake: Heat oven to 350 degrees . Grease and flour two 12-cup mini Bundt cupcake pans (2 1/2 inches across top). Prepare cake mix according to package directions with eggs and oil, but using buttermilk in place of water. Spoon batter into prepared pans, filling halfway full (about 2 tbsp batter in each).
2. Bake at 350 degrees for 15 to 20 minutes or until golden brown and a toothpick inserted in center comes out clean. Transfer to a wire rack; cool in pans for 5 minutes. Invert and cool completely. Use a small serrated knife to trim domed top from each cake to make level.
3. Tint vanilla frosting orange, if desired. Spread a small amount of frosting on top of trimmed side of a cake. Place another trimmed cake, cut-side down, on top of frosting to make a small pumpkin shape. Repeat to make 12 mini cakes.
4. Decorate: For frosted cakes, spread some of the frosting all over a mini cake to cover. Use a small spatula to spread frosting in ridges, starting from bottom to top. Add a trimmed candy bar piece on top as the stem.
5. For sugared cakes, microwave corn syrup for 3 to 5 seconds. Brush over an assembled cake, then roll cake in colored sugar to coat lightly. Add a candy or pretzel stem on top.
6. For glazed cakes, microwave 1/4 cup of the frosting for 5 to 7 seconds until smooth but not too thin. Spoon a little on top of a mini cake, allowing it to drip down the side. Add sprinkles while frosting is still wet. Add a trimmed candy or pretzel piece on top as stem.
7. Repeat recipe with the other flavor of cake mix, if desired.