Preheat oven to 300℉.

Spread the Lucky Charms cereal (no marshmallows) onto a lined 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 and save the milk and discard the cereal.

Preheat oven to 350℉.

Line one and a half muffin trays with cupcake liners and set aside.

In a small bowl, whisk together the flour, baking powder, cornstarch and salt. Set aside.

In a large bowl, beat together the butter, oil and sugar for 2 minutes until light-colored.

Beat in the eggs, vanilla extract and ¾ cup of the reserved cereal milk.

Beat in the dry ingredients until just incorporated.

Scoop the cupcake batter into the prepared liners using a ⅓ cup measuring cup and bake for 24-28 minutes, until an inserted toothpick comes out clean.

Allow the cupcake to cool completely before frosting.

In a large bowl, beat together the butter, 3 cups of the powdered sugar, 2 tablespoons of the cereal milk and the vanilla extract. Beat for 2 minutes before adjusting the texture with additional powdered sugar, if needed.

Scoop the frosting into a piping bag fit with a large star tip.