Preheat the oven to 350°F and line 2 large baking sheets with parchment paper or reusable baking mats. Separate the marshmallows from the cereal. Collect ¾ cups of the marshmallows and about 1 ½ cups of the cereal without marshmallows. Set the marshmallows aside and use a food processor or high-powered blender to grind the cereal up into a fine dust. You will need ¾ cup of the ground cereal. ¾ cup Lucky Charms marshmallows, ¾ cup ground up cereal, without the marshmallows
To a large mixing bowl, add softened butter and sugar. Use a hand mixer on high to cream together until light and smooth (about 2-3 minutes).
½ cup softened unsalted butter, ¾ cup granulated sugar
Add the egg and vanilla extract and use your hand mixer on low to combine.
1 large egg, 1 teaspoon vanilla extract
Add the ground up cereal, flour, salt, and baking soda and mix to combine, careful not to overbeat. Use a spatula to scrape any flour off the sides of the bowl and integrate it into your dough.
¾ cup all-purpose flour, ½ teaspoon baking powder, ½ teaspoon salt
Set aside a handful of marshmallows and use a rubber spatula to fold the rest into the dough to combine.
Use a large cookie scoop or 2 heaping tablespoons of dough to form your cookies, adding them to the prepped baking sheets. Leave at least an inch of space in between each cookie for minor spreading. Bake for 13-16 minutes on the top rack. Remove from the oven and while they are still hot, push the extra marshmallows into the top. Allow to cool and enjoy!