Preheat your oven to 350°F (convection).

In a stand mixer (or using a hand mixer), beat your room temperature butter for 3–5 minutes, until it turns light and slightly off-white. This helps create a soft, fluffy cookie base.

Add in your granulated sugar and beat for about 2 minutes, until the mixture becomes light and fluffy.

Add your egg and mix until fully combined.

Stir in your vanilla extract, making sure everything is evenly incorporated.

Add in your flour, baking powder, baking soda, and salt.

If using a stand mixer, mix on low speed just until combined.

If mixing by hand, gently fold together with a spatula.

Once your dough forms, fold in the Lucky Charms cereal and white chocolate chunks or chips.

Scoop cookie dough balls (about 1/3 cup each) onto a parchment-lined baking sheet, spacing evenly apart.

Bake for 11–13 minutes, or until the edges are set and the centers look just baked.

For perfectly circular cookies, place a round cup or bowl over each cookie immediately after baking and gently swirl it around to smooth the edges.

Let cookies sit on the baking sheet for about 10 minutes before transferring to cool completely.

Beat your butter until light and off-white.

Gradually add in powdered sugar and mix until fully incorporated.

Add your heavy cream and vanilla extract, then whip until light and fluffy.

If desired, gently stir the frosting with a spatula at the end to remove excess air bubbles (this helps when piping).

Lastly, whip in the marshmallow fluff until smooth and fluffy.

Transfer frosting to a piping bag to pipe a swirl, or spread with a knife/spatula.

Top with extra Lucky Charms cereal.

Enjoy fresh, store in the fridge for up to 10 days, or keep at room temperature for up to 1 week.