Preheat oven to 350°. Line a large baking sheet with parchment paper, or non stick spray.
Sort Lucky Charms cereal so you have 1 cup of marshmallows (plus more for adding on top of the cookies if you want) and 1/2 cup of cereal crushed. Set marshmallows aside.
You can crush the cereal using a food processor, blender, or adding it to a ziplock bag and crushing until no large pieces remain. Set aside.
In a large bowl in stand mixer with paddle attachment or handheld mixer, beat butter and sugar together until light and fluffy.
Add in the egg and vanilla, mix until well incorporated.
In a large bowl whisk flour, baking soda, baking powder, salt and crushed cereal together.
Pour dry ingredients into the wet and mix well.
Carefully fold in luck charms marshmallows.
Using a cookie scoop/ ice cream scoop thats about
Push some extra marshmallows on top of each cookie dough ball. This is optional but it gives the cookies an extra pop of color!
Bake in preheated oven for 12-15 minutes, or until the bottoms are golden brown.
The cookies will look and feel uncooked and really soft, but they will firm up as they cool.
Enjoy! Store the rest in an air tight container.