• In a medium bowl mix together the flour, cornstarch, baking soda and salt. Set aside.
• In the bowl of a mixer cream together the butter and both sugars. Mix until creamy and lighter in color. This should take 2 minutes. Mix in the egg and vanilla extract. Scraping the bowl as needed. Mix until fully combined.
• Slowly add the dry ingredients to the wet ingredients, mixing just until combined.
• Line a baking sheet with parchment paper and scoop out the cookie dough using a 1-ounce portion scoop, or 2 heaping tablespoons. Place 2 inches apart. Place in the refrigerator and chill the cookie dough for 2 hours.
• Preheat an oven to 350° F and bake the cookies for 14 minutes. Cool completely on cooling rack before frosting.

Buttercream Frosting

• In the bowl of a mixer add the butter and mix on medium speed until the butter is creamy and smooth.
• Slowly add in the powdered sugar, mixing on low to start then on medium speed until fully incorporated. Be sure to scrape down the sides of the bowl a few times.
• Add in the vanilla extract, salt and heavy cream. Turn the mixer to medium speed and mix for 1 minutes.

Assembly

• Scoop the frosting into a piping bag or use a spoon. Put a good amount of frosting on half of the cookies (the bottoms). Place another cookie on the top, slightly press down.
• Holding the cookie sandwich over the sprinkles, sprinkle them over, turning the cookie sandwich until all of the frosting has been covered. Enjoy!