Black and White Cookies
Recipe: https://recipestripper.com/recipes/9fbed103-7e12-4f3c-9618-60bcf385b346
Original source: https://www.americastestkitchen.com/recipes/6891-black-and-white-cookies

These huge, tender cookies may be New York’s best-kept secret. We spill it.
Yield: Makes 12 cookies
Total time: PT3H15M

Ingredients
- 1¾ cups (8¾ ounces/248 grams) all-purpose flour
- 1/2 teaspoon baking powder
- 1/4 teaspoon baking soda
- 1/8 teaspoon table salt
- 10 tablespoons unsalted butter, softened
- 1 cup (7 ounces/198 grams) granulated sugar
- 1 large egg
- 2 teaspoons vanilla extract
- 1/3 cup sour cream, divided
- 5 cups (20 ounces/567 grams) confectioners' sugar, sifted
- 7 tablespoons whole milk, divided
- 2 tablespoons corn syrup
- 1 teaspoon vanilla extract
- 1/2 teaspoon table salt
- 3 tablespoons Dutch-processed cocoa powder, sifted

Instructions
1. [FOR THE COOKIES:] Adjust oven racks to upper-middle and lower-middle positions and heat oven to 350 degrees. Line 2 baking sheets with parchment paper. Combine 1¾ cups (8¾ ounces) flour, ½ teaspoon baking powder, ¼ teaspoon baking soda, and ⅛ teaspoon salt in bowl.
2. [FOR THE COOKIES:] Using stand mixer fitted with paddle, beat 10 tablespoons softened unsalted butter and 1 cup (7 ounces) granulated sugar on medium-high speed until pale and fluffy, about 2 minutes. Add 1 large egg and 2 teaspoons vanilla and beat until combined. Reduce speed to low and add flour mixture in 3 additions, alternating with ⅓ cup sour cream in 2 additions (about 2½ tablespoons each), scraping down bowl as needed. Give dough final stir by hand.
3. [FOR THE COOKIES:] Using greased ¼-cup measure, drop cookie dough 3 inches apart onto prepared baking sheets. Bake until edges are lightly browned, 15 to 18 minutes, switching and rotating sheets halfway through baking. Let cookies cool on sheets for 5 minutes, then transfer to wire rack to cool completely, about 1 hour.
4. [FOR THE GLAZE:] Whisk 5 cups (20 ounces) confectioners’ sugar, sifted; 6 tablespoons milk; 2 tablespoons corn syrup; 1 teaspoon vanilla; and ½ teaspoon salt together in bowl until smooth. Transfer 1 cup glaze to small bowl; reserve. Whisk 3 tablespoons Dutch-processed cocoa powder, sifted, and remaining 1 tablespoon milk into remaining glaze until combined.
5. [FOR THE GLAZE:] Working with 1 cookie at a time, spread 1 tablespoon vanilla glaze over half of underside of cookie. Refrigerate until glaze is set, about 15 minutes. Cover other half of cookies with 1 tablespoon chocolate glaze and let cookies sit at room temperature until glaze is firm, at least 1 hour. Serve. (Cookies can be stored at room temperature for up to 2 days.)