Heat oven to 350 degrees F and line two cupcake tins with cupcake liners.
In a small bowl, mix the mini chocolate chips with 3 tablespoons of cake mix and set aside. In a large mixing bowl, add the remaining cake mix and pudding mix. Using a rubber spatula, mix together. Add vegetable oil, sour cream eggs, coffee, water and vanilla and mix together with a spatula. Using an electric mixer, mix the batter thoroughly until ingredients have incorporated. Occasionally use the rubber spatula to scrape the bottom and sides of the bowl. Add chocolate chips and stir with rubber spatula, just to combine.
Using a large cookie scoop, scoop batter into cupcake liners and bake for 18 to 20 minutes or until poking the center of several cupcakes with toothpick results in a clean toothpick. Allow to cool for 2 to 3 minutes in the cupcake tin. Carefully remove from cupcake tin using an angled spatula and allow cupcakes to cool on a cooling rack.
(Vanilla) Buttercream Dream
In the bowl of a stand mixer, add both butters and shortening and cream together at a medium speed. Then, add vanilla extract and mix thoroughly.
Add half of the confectioner's sugar with the stand mixer turned. Mix well at a low speed. Then, add the rest of the confectioner's sugar. The mixture may look crumbly or curdled. With mixer on at a low speed, add milk one tablespoon at a time. Add more for creamier and thinner frosting, use less milk for thicker frosting. Be sure to scrape down the sides of the bowl a couple of times. Once milk has been added, turn mixer to medium speed and allow to mix for 3 to 4 minutes.
Store in the refrigerator when not in use. Allow to sit on the counter for about 15 to 20 minutes and whip with angled spatula before adding to piping/decorator bags. Sometimes, I add a little bit of water to it while I'm whipping and it gives a nice creamy texture.
Chocolate Butterceam
In the bowl of a stand mixer, add butter and shortening and mix together on a medium speed. Add cocoa and vanilla and mix on low speed until combined. Add half of the confectioner's sugar and mix on a low speed. Add the rest and the mixture will probably look crumbly. One tablespoon at a time, add the milk until you get the consistency you want. Mix on medium speed for 3 to 4 minutes. Same with the vanilla buttercream, store in the refrigerator when you're not working with it.
Assembly
Set up your decorator bags I put my decorator bags inside a glass (I used a stemless wine glass). Measure out one cup of frosting and fill the bag with an angled spatula. Then, do the same in another decorator bag for your other color. Then, cut the tips of both bags at the same spot. Add rubber bands to the tops of both decorator bags, so the frosting doesn't go out the top when you squeeze them.
Fit your 16 inch decorator bag with a large open star tip. Add both color frosting bags to the larger one and make sure both of the frosting colors match up inside the star tip.
To frost the cupcake, lace the tip at a 90 degree angle on top of the cupcake off to the side. Keeping the same angle and with an even pressure, squeeze the decorator bag while moving in a clockwise motion about two or three times. When you're near the end, pull away and stop squeezing to get the finished swirled frozen yogurt look. Repeat for the remaining cupcakes.
This will frost about 5 to 7 cupcakes depending on how much frosting you use. To frost the rest of the cupcakes, you'll need to remove the smaller bags and refill them. It may get a little messy and you may need to clean the inside of the start tip or use fresh new 12 inch bags.
For a quick demo of frosting these cupcakes, check out my video.