Heat oven to 350 degrees. Spray a standard muffin tin with non-stick cooking spray or line with cupcake liners.
To prepare the cupcakes, add the cake mix to a large mixing bowl. Using a hand or stand mixer, mix the oil, water, and egg whites on medium speed until well incorporated.
1 box French Vanilla cake mix, 1/3 cup vegetable oil, 1 1/4 cups water, 4 egg whites
Slowly mix in a couple drops of the bubble gum extract. It's very strong so you won't want to add much more than that.
2-3 drops bubblegum extract
Divide the batter evenly into three bowls. Color one with pink food coloring, one with purple and one with blue.
Food coloring gel
Add a spoonful or two of each color to your lined muffin tin. Each one should be about 2/3 full.
Use a toothpick or a butter knife to gently swirl the colors together.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Place the cupcakes on a wire rack and allow them to cool completely before frosting.
For The Frosting
In a large bowl, use a hand or stand mixer on low speed to cream the butter for about two minutes. It should be light and fluffy.
1 cup salted butter
Add the vanilla extract and mix well.
1 teaspoon vanilla extract
Slowly mix in 1 cup of the powdered sugar followed by 1 tablespoon of the half and half. Continue to alternate mixing in the powdered sugar and half and half until the frosting is creamy and stiff peaks have formed.
3-4 cups powdered sugar, 3 tablespoons half and half
Separate the frosting into three bowls. Add pink food coloring to one, purple to another and teal or blue to the third, mixing until you get the desired color. Use a little less food coloring for pastel colors and more for brighter colors.
Food coloring
Add each frosting color to it's own small piping bag. Then, insert all three of the smaller bags into a large piping bag fitted with a star tip.
Be sure your cupcakes have cooled completely, then frost each one. It's a good idea to squeeze a little frosting onto a plate until you get a good combination of colors (you may just get one color at first).
Finally, add your unicorn toppers. I used this set from Amazon. They also came with some really cute cupcake wrappers, but because they hid a lot of the frosting, I displayed most of the cupcakes without them.
Notes
Be careful not to overmix your batter. It could cause your cupcakes to be dense and tough so you'll want to mix until ingredients are just combined.
If your frosting is too runny, add a little extra powdered sugar. If it's too thick, add a little more Half & Half. Just use a little at a time, until you get the desired consistency.
Be sure the cupcakes have cooled completely before frosting. If you frost them while still warm, the frosting could melt right off.
Chilling your frosting slightly can help it hold its shape better when piping.