Black and White Cookies

Bahan-bahan (12 porsi)

• 1 and 3/4 cups (219g) all-purpose flour (spooned & leveled), or more as needed, see note*
• 1/2 teaspoon baking powder
• 1/4 teaspoon baking soda
• 1/4 teaspoon salt
• 10 Tablespoons (142g) unsalted butter, softened to room temperature
• 1 cup (200g) granulated sugar
• 1 large egg, at room temperature
• 2 teaspoons pure vanilla extract
• 1/3 cup (80g) full-fat sour cream, at room temperature*
• 5 and 1/2 cups (660g) confectioners’ sugar, sifted (measure before sifting)
• 7 Tablespoons (105ml) whole milk, divided
• 2 Tablespoons light corn syrup
• 1 teaspoon pure vanilla extract
• 1/2 teaspoon salt
• 3 Tablespoons (15g) unsweetened natural or dutch-process cocoa powder