Ingredients:

  • 1 cup (16 Tbsp; 226g) unsalted butter, softened to room temperature
  • 1 and 1/2 cups (300g) granulated sugar
  • 1 egg + 1 egg yolk, at room temperature
  • 2 teaspoons pure vanilla extract
  • 3 cups (375g) all-purpose flour (spooned & leveled)
  • 1 and 1/4 teaspoons baking soda
  • (Optional) cream of tartar - amount not specified in recipe.
  • 1 teaspoon cornstarch
  • 1/2 teaspoon salt
  • 1 cup sprinkles, plus more for decorating on top of frosting
  • 3/4 cup (12 Tbsp; 170g) unsalted butter, softened to room temperature
  • 2 and 1/4 cups (270g) confectioners sugar
  • 3 Tablespoons (45ml) heavy cream or half-and-half
  • 1 teaspoon pure vanilla extract
  • 1/8 teaspoon salt

Instructions:

  1. In a large bowl using a handheld mixer or stand mixer fitted with a paddle attachment, beat the softened butter on medium speed until smooth—about 1 minute.
  2. Add granulated sugar and continue beating until fluffy and light in color.
  3. Mix in the egg, egg yolk, and vanilla extract. Scrape down the sides of the bowl as needed.
  4. In a separate medium bowl, whisk together flour, baking soda, cream of tartar, cornstarch, and salt.
  5. With your mixer running on low speed, gradually add dry ingredients to wet ingredients in three parts. The dough will be thick but will come together after mixing thoroughly.
  6. Gently fold in sprinkles on low speed until evenly distributed.
  7. Cover dough tightly with plastic wrap and chill in refrigerator for at least 3 hours or up to 3 days. Chilling is mandatory!
  8. When ready to bake: Let cookie dough sit at room temperature for 15–40 minutes depending on chilling time before continuing.
  9. Preheat oven to 325°F (163°C) and line two large cookie sheets with parchment paper or silicone mats.
  10. Scoop out about 1.5 tablespoons of dough per cookie ball; place approximately 8–9 cookies per sheet.