Ingredients:
- 1 cup (227g / 8 oz) unsalted butter, softened
- ¾ cup (150g / 5.3 oz) granulated sugar
- ¾ cup (165g / 5.8 oz) packed light brown sugar
- 2 large eggs
- 2 teaspoons pure vanilla extract (10 mL)
- 2 ¼ cups (281g / 10 oz) all-purpose flour
- 1 teaspoon baking soda (5 mL)
- 1 teaspoon cornstarch (5 mL)
- ½ teaspoon salt (2.5 mL)
- 1 cup (170g / 6 oz) sprinkles, rainbow or your choice
- 1 cup (227g / 8 oz) unsalted butter, softened
- 3-4 cups (360-480g / 12.7-16.9 oz) powdered sugar, sifted
- 3-4 tablespoons (45-60 mL) milk or heavy cream
- 2 teaspoons pure vanilla extract (10 mL)
- Pinch of salt
- Sprinkles for decorating (optional)
Instructions:
- Cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.
- Beat in the eggs one at a time, then stir in the vanilla extract.
- In a separate bowl, whisk together the flour, baking soda, cornstarch, and salt.
- Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix!
- Gently fold in the sprinkles.
- Cover the dough and chill in the refrigerator for at least 30 minutes. This prevents the cookie from spreading too thin while baking.
- Preheat oven to 350°F (175°C). Line a 12-inch pizza pan with parchment paper.
- Press the chilled dough evenly into the prepared pan, leaving about a 1/4-inch border.
- Bake for 25-30 minutes, or until the edges are golden brown and the center is set (slightly soft is okay!).
- Let the cookie cake cool completely in the pan before frosting.
- While the cookie cools, beat the softened butter until light and fluffy. Gradually add the powdered sugar, alternating with the milk, until smooth and creamy. Stir in the vanilla and salt.
- Frost the cooled cookie cake with the buttercream frosting using an offset spatula or butter knife.
- Decorate with additional sprinkles, if desired.
- Slice and serve immediately, or store in an airtight container. Enjoy your birthday cake cookie cake!