Instructions

COOKIE CAKE

1. Adjust an oven rack to the center of the oven. Heat oven to 350 degrees. Line the bottom of a 9-inch round cake pan with parchment paper and spray the sides with nonstick baking spray.
   
   
2. In the bowl of a stand mixer, fitted with the paddle attachment, cream together the butter and sugar on medium-high speed until light and fluffy, about 4 minutes. Add egg and vanilla extract and mix to combine. In a medium bowl, whisk the flour, baking soda, cornstarch and salt to combine. Add the dry ingredients to the wet ingredients and mix to combine. Give the dough a few stirs by hand with a rubber spatula to bring together. Stir in the white chocolate chips and sprinkles.
   
   
3. Press the dough evenly into the prepared cake pan and press a few more white chocolate chips into the top of the cookie. Bake the cookie for 20 to 22 minutes or until the edges start to lightly brown. The center my jiggle slightly, but will firm up while it cools.
   
   
4. Allow the cookie cake to cool in the cake pan on a wire rack for 2 hours. Once the cookie is cool, invert the cookie onto a cake board or large plate, then invert onto a serving platter.

BUTTERCREAM

1. Beat the butter and shortening in a large bowl until smooth. Add 1 cup of powdered sugar and mix until combined. Add the vanilla extract and water and mix until smooth. Add the remaining cup of powdered sugar and mix until combined.
   
   
2. Add as much or as little gel color to the frosting to achieve your desired color. Fill a piping bag with a piping tip of your choice and pipe along the edges of the cookie in a decorative fashion. Finish the edges off with a few July 4th sprinkles .