Preheat the oven to 350F. Line two large cookie sheets with parchment paper.
In a medium bowl, whisk together the all purpose flour, baking powder, and salt. Set aside.
2 ¾ cups all purpose flour, 2 teaspoons baking powder, ½ teaspoon fine sea salt
In the bowl of a stand mixer fitted with the paddle attachment, beat together the butter, brown sugar and granulated sugar on medium speed until light and fluffy, 3-5 minutes, stopping to scrape down the sides and bottom of the bowl with a spatula halfway through mixing.
1 cup unsalted butter, room temperature, ½ cup light brown sugar, packed, ⅓ cup granulated sugar
Beat in the vanilla. Beat in the eggs one at a time, scraping down the sides and bottom of the bowl after each addition.
2 teaspoons pure vanilla extract, 2 large eggs, room temperature
Beat in the flour mixture until just combined.
Remove the bowl from the mixer, and fold in the marshmallows.
1 cup Lucky charms marshmallows
Portion the dough using a ¼ cup (2oz) ice cream scoop. Form the dough balls into thick discs, about ½" thick and place 3" apart on the cookie sheets, 6 cookies on each sheet.
Bake the cookies for 10-11 minutes, or until the edges start to turn light golden and the top no longer looks shiny. Rotate the cookie sheets halfway through baking, or bake the cookies one pan at a time. Do not over bake. Cool completely on the cookie sheets.
While the cookies cool, prepare the frosting. In the bowl of a stand mixer fitted with the paddle attachment, combine the butter, sugar, milk, vanilla and salt. Mix on medium-low speed for one minute. Scrape down the sides and bottom of the bowl.
½ cup unsalted butter, room temperature, 1 ¼ cups confectioners sugar, 1-2 tablespoons milk, 1 teaspoon pure vanilla extract, pinch of salt
Add the gel food color and turn the speed up to medium high. Beat the frosting for 3-5 minutes until light and fluffy.
1-2 drops pink gel food color
Optionally, transfer the frosting to a piping bag fitted with a large round piping tip. Pipe frosting onto the center of each cookie. Use a spatula to spread the frosting over the cookie. Top the cookies with more cereal. Enjoy!
Lucky Charms cereal, for topping