A cast iron skillet cookie recipe for a gigantic sugar cookie with rainbow sprinkles and homemade pink frosting. The sprinkles give the cake a funfetti vibe, making it perfect for birthday parties or other celebrations.
Grease a cast iron skillet (ours is 9.5 in) and set aside.
Stir together the flour, baking powder, baking soda and cornstarch in a small bowl. Set aside.
Using a mixer, combine the butter and sugar together until light and fluffy, about 2 minutes.
Add the egg, egg yolk and vanilla to the sugar-butter mixture and combine fully.
Add in the dry ingredients and mix until thoroughly combined, then add sprinkles to your desired preference.
Press the cookie dough into the skillet in an even layer.
Bake for 25-30 minutes until lightly golden on top.
Remove from oven and let cool as you prepare the frosting.
In a medium-sized bowl, combine the butter, icing sugar and vanilla together for 1 minute until smooth, then add 1 Tablespoon milk and mix for 30 seconds. Adjust texture as needed with additional sugar or milk.
Add pink food coloring as needed to reach desired shade of pink.
Scoop the frosting into a piping bag fit with a star tip.
Make dollops of frosting along the edge of the cookie, making short 2" swirls and pulling the piping bag back firmly. Top with a few sprinkles on each frosting dollop.