Preheat the oven to 350 degrees. Line a cupcake pan with the cupcake paper liners you choose. I suggest using gold paper cupcake liners to look like a pot of gold, but you can use any liners that you want to.

Place your self-rising flour, cake flour, and sugar in the bowl of your mixer. Mix them 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, and 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.

Add the eggs to the cake batter and mix until combined. Add in the green food coloring until you have the desired green color.

Scoop the batter into the prepared cupcake pan, filling each one 3/4 of the way full.

Bake for 10 minutes, then rotate the cake pans so the pan on the top rack is now on the bottom and the pan on the bottom is now on the top rack. Continue to bake for another 10-13 minutes until a toothpick comes out clean from the center of the cupcake.

Transfer the cupcakes to a cooling wire rack until they have reached room temperature.

Take the butter out and bring it to room temperature on the counter.

Add the butter and shortening and whip until they are both creamed together on medium speed in the bowl of a stand mixer with the paddle attachment or whisk attachment.

Once the butter and shortening are creamed and whipped ,lower the mixer speed to low and add the confectioner's sugar until it is all mixed in.

Once the confectioners’ sugar is all mixed in add the vanilla extract turn the mixer up to medium speed and leave the mixer mixing for 5-10 minutes until the frosting is light and fluffy.

Before fluffing the frosting at a higher speed, if you need to scrape the frosting down into the bowl, if it is on the side of the bowl, do so using a wooden spoon or a silicone utensil.

If you need to thicken the frosting, add a little bit of powdered sugar. If you need to thin the frosting then add hot water 1 tablespoon at a time while it is mixing until it is the desired thickness.

Cut the tip off of the pastry bag and add an extra-large star piping tip to the piping bag. Using the paintbrush, paint a line of each gel food coloring starting at the inside tip and going halfway up the bag, making sure you are going in the color order of the rainbow.

Then, carefully fill the bag with the buttercream. Pipe the buttercream in a swirl on each cupcake, as you pipe the buttercream frosting on the cupcake the food coloring will make a rainbow on the frosting.

Cut the tip off the second pastry bag and add the straight piping tip. Fill the bag with buttercream.

Pipe three small circles on the side of the cupcake and three small circles to the top of the cupcakes.

Cut the rainbow strips in half. Stick one side of the candy into each of the small dots of buttercream to create a rainbow shape.