Preheat the oven to 325 degrees F. Place the cupcake liners into the cupcake pan(s).

Place the sour cream, buttermilk, vanilla, eggs, and vegetable oil into a large mixing bowl. Whisk until smooth. Then sift in the cake mix, granulated sugar, and cocoa powder. Stir until smooth--but not overmixed. Do not skip sifting the cake mix because the batter will be lumpy.

Using a cookie scoop, divide and place the cake batter into the cupcake liners. Fill them about 1/2 - 2/3 full.

Bake for 15-17 minutes or until a toothpick inserted into the middle of a cupcake comes out clean or with a few small crumbs. Do not overbake. After 5 minutes of cooling time, move the cupcakes to a cooling rack. Cool completely before frosting.

Use a mixer to beat the butter, vanilla, butter flavoring, and salt until creamy. Add the cream and stir. Add the powdered sugar a cup at a time and beat between each addition.

Divide the frosting in half, leaving one half in the mixing bowl and placing the other half in a separate bowl.

Add a few drops of Leaf Green gel coloring to the frosting in the mixing bowl and beat it to mix the color well. Keep adding Leaf Green, if necessary, to make a rich green color. Then add a couple of drops of Kelly Green gel coloring and beat until the frosting is a vivid green color reminiscent of Frankenstein or St. Patrick's Day green. Move the finished green frosting from the mixing bowl to another bowl and set it aside for piping later. (Be sure to get as much of the frosting off the beater as possible.)

Add the other half of the white frosting back into the mixing bowl. Do not wash the mixing bowl or beater because the chocolate will cover any green frosting. Add dark chocolate cocoa powder and beat until well mixed. Add black gel food coloring (or charcoal powder) to the buttercream and mix. Keep adding gel coloring or charcoal (it takes a lot) until the frosting is black. You can use gel coloring and charcoal powder to dye the frosting black. Beat in a little extra cream if the frosting is too stiff.

Place the star tip into a piping bag with the end snipped off. Use a frosting coupler with the piping bag to make it easy to change the star tip to another color. (See note below for a link on how to use a coupler.) Fill the bag with green frosting. Pipe green frosting onto half of the cupcakes. Spoon the sprinkles over the buttercream of each cupcake as you finish frosting them. If you frost all the cupcakes before you add the sprinkles, the frosting will crust slightly, making it hard for the sprinkles to stick. Tap down any loose sprinkles.

Change and wash the tip and set up another piping bag. (Or use another Wilton 1M tip.) Add the black buttercream to the bag. Pipe chocolate frosting onto the other cupcakes. Spoon sprinkles over each cupcake, pressing them into the frosting if necessary to make them stick.