Preheat the oven to 350 degrees. Line your cupcake pans with your choose of cupcake wrappers.
Place your self-rising flour, cake flour, and sugar in the bowl of your mixer. Mix them together for a minute or two until they are well combined.
Cut your butter into tablespoon pieces. Slowly add your butter into the flour mixture one piece at a time continue mixing until you have reached the texture of sand.
Pour half of your milk into the flour mixture and mix just until the milk is incorporated. Use your rubber spatula to scrape down the sides of your bowl. Add your remaining milk and the vanilla to your batter and mix until combined.
Slowly add in one egg at a time to the cake batter, making sure each egg is incorporated before adding the next egg.
Scoop the batter into the prepared cupcake pan, filling them 3/4 of the way full.
Bake for 10 minutes then rotate the cake pans so the pan that was on the top rack is now on the bottom and the pan that was on the bottom is now on the top rack. Continue to bake for another 10-13 minute until a toothpick comes out clean from the center of the cupcake.
How to Make Vanilla buttercream Frosting
Place your butter and shortening together in the bowl of your mixer. Mix them together on medium speed until they are nice and creamy.
Turn the mixer down to the lowest setting and slowly incorporate the powdered sugar into the shortening mixture.
Once you have added all the powdered sugar in to your mixture, add in the vanilla extract and then the hot water.
Turn the mixer up to medium-high speed and continue mixing for 10 minutes until light and fluffy.
How to make Big Hero 6 Cupcakes
Bake your cupcakes and let them cool. While the cupcakes are cooling make a batch of buttercream frosting.
Place your large piping tip into your pastry bag and then fill the bag with your buttercream frosting.
Swirl the buttercream in a single layer starting in the middle of the cupcake working your way out to the edge and repeat onto each cupcake.
Mix 1 cup of buttercream with a few drops of black food coloring until you get a nice black buttercream. Place the small tip into a clean pastry bag and the black buttercream.
Pipe out one small circle then a line and end with another small circle at the end of the line, repeat this on each cupcake.