Who doesn’t like cupcakes on their birthday?! The milk that is added to these cupcakes has been soaking in cereal to kick up the flavor. It replicates the sweet milk at the bottom of the cereal bowl – aka, the best part!
In a small bowl stir together the milk and cereal until combined. Let soak for at least 1 hour and up to overnight. Strain the milk using a fine mesh strainer then stir in the brown sugar and salt. Refrigerate until ready to use.
For the birthday cupcakes:
Preheat the oven to 350ºF (180ºC). Line a 12-cup standard-size muffin tin with paper liners.
In a large bowl, sift together the flour, baking powder and salt. In the bowl of a stand mixer fitted with a paddle attachment, beat together the sugar and butter on medium speed until the mixture is light and fluffy, about 3 minutes. Reduce the speed to low and add the eggs, beating well. Add the vanilla and beat until combined.
Alternate slowly adding the milk and flour into the mixture and beat completely combined, about 30 seconds. Gently stir in the rainbow sprinkles so they are evenly distributed.
Evenly divide the batter among the prepared muffin cups, filling each so they are about ¾ full. Bake the cupcakes until the tops are golden brown and a toothpick inserted into the middle of a cupcake comes out clean, about 20 to 25 minutes.
Transfer the cupcakes to a cooling rack and let cool completely.
For the frosting:
In the bowl of a stand mixer fitted with the whisk attachment beat the shortening for 20 seconds so that it is creamy on medium speed. Lower the speed of the mixer and add the confectionary sugar one cup at a time, beating well after each addition. Once all the sugar has been incorporated beat in the vanilla and milk.
Spoon the frosting into a piping bag fitted with a medium star tip. Working one cupcake at a time and starting from the outside edge, slowly pipe the frosting around the edge of the cupcake. Start to spiral the frosting inward as you pipe, finishing in the middle with a small peak.