¾ cup (170 grams) unsalted butter, room temperature¾ cup (150 grams) granulated sugar½ cup (110 grams) firmly packed light brown sugar1 large egg (50 grams), room temperature1 large egg yolk (19 grams), room temperature1 tablespoon (13 grams) vanilla extract3 cups (375 grams) all-purpose flour2½ teaspoons (12.5 grams) baking powder½ teaspoon (1.5 grams) kosher salt½ cup (80 grams) plus 1 tablespoon (10 grams) rainbow sprinkles*Vanilla Buttercream (recipe follows)Garnish: rainbow sprinkles
Vanilla Buttercream
2 cups (240 grams) confectioners’ sugar4 teaspoons (20 grams) heavy whipping cream1 teaspoon (6 grams) vanilla bean paste⅛ teaspoon kosher salt
Sprinkle Sugar Cookie
Preheat oven to 350°F (180°C). Spray a 9-inch round cake pan with baking spray with flour.
Assemble the Ankarsrum with the stainless steel bowl. Place the dough knife in the smaller hole, and position the dough roller just off the side of the bowl. Beat butter by slowly increasing mixer speed to medium-high (6 o’clock) until creamy, about 1 minute, using the scraper to help move butter around. (Butter might stick to the roller in the beginning.) Slowly add sugars, scraping bowl frequently. Let mix until well combined and lightened in color, about 3 minutes. Add egg and egg yolk, beating until just combined. Beat in vanilla.
In a medium bowl, whisk together flour, baking powder, and salt. With mixer on the lowest speed (12 o’clock), gradually add flour mixture to butter mixture. Move roller to 1 inch away from side of bowl, and increase mixer speed to medium-low (2 o’clock), mixing until combined. Gently fold in ½ cup (80 grams) sprinkles by hand. Press batter into prepared pan. Sprinkle top with remaining 1 tablespoon (10 grams) sprinkles.
Bake until center is set and a wooden pick inserted in center comes out clean, about 30 minutes. Let cool completely in pan. Remove from pan.
Place half of Vanilla Buttercream in a pastry bag fitted with a round piping tip (Ateco #805). Place remaining buttercream in a pastry bag fitted with a small open star piping tip (Ateco #822). Alternate piping rounds and stars around edge of cookie. Garnish with sprinkles, if desired.
Vanilla Buttercream
Assemble the Ankarsrum mixer with the beater bowl and ballon whisks. Beat butter at medium-low speed (2 o’clock) until smooth. Gradually add confectioners’ sugar, beating until well combined and stopping to scrape sides of bowl. With mixer on low speed (12 o’clock), add cream, vanilla bean paste, and salt, beating until combined. Increase mixer speed to medium (4 o’clock), and beat for 1 to 2 minutes. Use immediately.
