Ingredients
1cupunsalted butter,(230 grams), softened to room temperature
1½cupsgranulated sugar,(300 grams)
1egg,plus 1 yolk, at room temperature
2tsppure vanilla extract
3cupsall purpose flour,(360 grams), spoon & leveled
1¼tspbaking soda
½tspcream of tartar
1tspcornstarch
½tspsalt
1cupsprinkles,plus more for decor on top of frosting
¾cupunsalted butter,(170 grams), softened to room temperature
2¼cupsconfectioner’s sugar,(270 grams)
3tbspheavy cream,(45 milliliter), or half and half
1tsppure vanilla extract
⅛tspsalt
Preparation
In a large bowl using a hand-held mixer or stand mixer fitted with a paddle attachment, cream the softened butter for about 1 minute on medium speed.
Get it nice and smooth, then add the sugar on medium speed and beat until fluffy and light in color. Beat in egg, egg yolk, and vanilla. Scrape down the sides and up the bottom of the bowl as needed.
In a medium bowl, whisk the flour, baking soda, cream of tartar, cornstarch, and salt together until combined.
With the mixer running at low speed, slowly add the dry ingredients to the wet ingredients in 3 different parts. Once combined, gently beat in the sprinkles at low speed until evenly disbursed.
Cover the cookie dough tightly and chill in the refrigerator for at least 3 hours and up to 3 days. Chilling is mandatory.
Remove cookie dough from the refrigerator and let sit out at room temperature for at least 15 minutes. If the cookie dough chilled longer than 3 hours, allow to sit at room temperature for 30 to 40 minutes.
Preheat oven to 325 degrees F (163 degrees C) and line 2 large cookie sheets with parchment paper or silicone baking mats.
Roll cookie dough into balls, about ½ Tablespoons of dough in each ball, and set on a cookie sheet, about 8 to 9 cookies per sheet.
Bake in batches for 11 to 12 minutes or until the edges are slightly browned. Allow the cookies to cool on the cookie sheets for 3 minutes, then move to a wire rack to cool completely.
In a large bowl using a hand-held mixer or stand mixer fitted with a paddle attachment, beat the butter on medium speed until creamy for about 2 minutes.
Add confectioners’ sugar, cream, vanilla extract, and salt with the mixer running on low. Increase to high speed and beat for 3 full minutes.
Add more confectioners’ sugar if frosting is too thin, more cream if frosting is too thick, or a pinch more of salt if frosting is way too sweet.
Frost the cooled cookies as desired and decorate with more sprinkles.
Store cookies in an airtight container at room temperature for up to 3 days or in the refrigerator for up to 6 days.
