In a bowl, combine the heavy cream and lucky charm cereal to start the frosting. Set aside.
Preheat your oven to 350°.In the bowl of a stand mixer, cream together the butter and sugar for 1 minute.
Scrape the sides of the bowl and add in the eggs, vanilla extract and canola oil. Mix until well combined.
Add in the flour and baking powder. Mix until a soft dough forms.
Mix in the lucky charm marshmallows.
Scoop the cookie dough out in a heaping 1/3 cup portions. Roll into a ball and flatten just slightly. The cookies will spread and flatten as they bake.
Repeat with the remaining dough.Arrange on a parchment paper or silicone baking mat covered pan. Place 6 cookies on each tray.
Bake at 350° for 14-16 minutes.
When the cookies are done, The cookies will spread and the center of the cookie should look puffed up and no longer wet before taking them out of the oven.
Allow the cookies to cool completely on the pan before continuing.
Once the cookies are cool, make the frosting by first, adding the milk to the heavy cream and cereal, thinning out the heavy cream.
Strain the soggy cereal out of the heavy cream to make the 'cereal milk'. Set aside.
Next, combine the butter, powdered sugar and the cereal milk. Whip until the frosting is light and fluffy.
Divide the frosting among the cookies and spread smooth.Top with approx 1/8 cup of cereal.
Refrigerate for 15-20 minutes before serving.