• Preheat oven to 350°F and line two cookie sheets with parchment paper or silicone mats.
• In the bowl of a stand mixer fitted with paddle attachment or in a large bowl with electric hand mixer, cream softened butter and granulated sugar together until light and fluffy. This takes about 2-3 minutes.
• Add the eggs one at a time, beating well after each egg and scraping sides of the bowl with rubber spatula as needed.
• Then mix in the the vanilla extract.
• Add the baking powder, salt and all purpose flour. Mix on low speed until everything is just barely evenly combined.
• Fold in the marshmallow cereal or mix it in on low speed just until combined.
• Using a ⅓ cup or a scant 3.25 oz cookie scoop, make 12 cookie dough scoops and place 6 on each prepared baking sheet.
• Roll the cookie dough into balls and flatten slightly with the palm of your hand so they look like thick hockey pucks.
• Bake cookies one pan at a time on center rack for 14-16 minutes until edges are barely golden brown and the centers no longer look wet and glossy.
• Let cookies cool on sheet pans for 5 minutes then transfer to a wire rack to cool completely.
• While the cookies are cooling make the cereal milk buttercream frosting.

Cereal Milk Frosting

• Combine ¾ cup cereal with ½ cup milk in a cereal bowl and set aside.
• In a stand mixer with the paddle attachment or whisk attachment, cream softened butter until smooth.
• Add the powdered sugar, one cup at a time, mixing until fully incorporated after each cup.
• Mix in the vanilla extract.
• Strain the milk from the cereal.
• Add the cereal milk and mix in. Once it's all combined bump up the speed to medium and beat until light and airy, about 1-2 minutes, while scraping the sides of the bowl a few times.
• Once the cookies are completely cooled, evenly distribute the frosting with a cookie scoop and dollop the frosting on top of each cookie.
• Using an offset spatula or butter knife spread the frosting over top of the cookies.
• Top cookies with remaining cereal, either crushed or whole and lightly press them down. Let the cookies rest until the frosting has set.