Lucky Charms cake combines your favorite cereal with a sweet (green!), fluffy cake, and a decadent, cereal-inspired buttercream frosting for a dessert that is magically delicious! Perfect St. Patrick's Day cake or a fun treat any time of the year!
Preheat oven to 300ºF and line a baking sheet with parchment paper or a silicone baking mat.
Remove the marshmallows from the Lucky Charms cereal and reserve them for later.
Spread the Lucky Charms cereal (no marshmallows) onto the baking sheet and bake for 15 minutes, stirring halfway. Allow cereal to cool.
Place the cooled cereal and milk in a large bowl and allow to soak for 15 minutes.
Drain, saving the milk and discarding the cereal.
Make the Cake
Preheat oven to 350ºF. Line a 9 x 13 baking pan with parchment paper and coat with non-stick spray. Set aside.
In a medium bowl, whisk to combine the flour, baking powder, cornstarch, and salt. Set aside.
In a large bowl, beat together the butter, oil, and sugar until light-colored and fluffy, about 2 minutes. Beat in the eggs, vanilla extract, and ¾ cup of the reserved cereal milk.
With the mixer on low, add the dry ingredients and mix until just incorporated.
Mix in the green food coloring, if desired.
Pour the batter into the pan and bake for 28-32 minutes, or until an inserted toothpick comes out mostly clean.
Allow the cake to cool completely before frosting.
Make Frosting & Decorate
In a large bowl, beat together 3 cups of confectioners sugar, butter, cereal milk, and vanilla extract for 2 minutes or until smooth and well-combined. If frosting is too thin add additional confectioners sugar by the Tablespoonful, as needed.
Spread the frosting over the cooled cake and top with sprinkles and your reserved Lucky Charms marshmallows.
Notes
Cover and store at room temperature or in the fridge for up to three days.
Not a fan of sheet cakes? Divide the batter into 2 square or round pans to create a layer cake. Be mindful that it will take less time to bake however, so keep an eye on them in the oven.