Preheat oven as per directions on the box and place 24 cupcake liners in cupcake pans. Set aside.

Make the cupcakes according to the box instructions.

Divide the batter into two bowls and mix green food coloring into one of the bowls. Remember you can always add more coloring but not take it away!

Alternate between the green batter and the plain one and place about one tablespoon of each batter into the cupcake liners until two-thirds full.

Cook for as long as directed or until a toothpick inserted into the center of the cupcakes comes out clean.

Allow the cupcakes to cool in the pan for a few minutes before transferring to a wire rack to cool completely before frosting.

To make the frosting, use an electric mixer to combine the butter, cream cheese, powdered sugar, heavy whipping cream, and vanilla on medium speed until combined and smooth, stiff peaks form.

Scoop out one-quarter cup of frosting into a small bowl and color with green food coloring gel to get a light green shade. Remember you can always add more coloring, but not take it away!

Scoop green frosting into one half of a large piping bag fitted with a large star tip, then scoop the remaining frosting into the other half. Squeeze out some frosting to make sure colors have combined, then pipe swirls onto the cooled cupcakes.

Place the unicorn horn icing decoration in the top center of the frosting and place an ear on either side of the horn. Add the closed eye sprinkles just below the ears.

Add some St. Patrick's Day sprinkles around the horn and ears of the cupcakes to finish off.