The iconic black and white cookie with its half-vanilla, half-chocolate frosting is a beloved New York bakery classic. This soft, cakey cookie is a must-try family treat.
Preheat your oven to 350°F. Line two baking sheets with parchment paper for even baking and easy cleanup.
Whisk together the flour, baking powder, and baking soda in a medium bowl, ensuring no lumps for a soft, cakey texture.
In a large bowl, cream unsalted butter and granulated sugar until pale and fluffy using medium speed; then add eggs one at a time, mixing well after each.
Add sour cream, milk, and vanilla extract to the creamed mixture. Blend until just combined and gradually mix in the dry ingredients for a smooth batter.
Scoop ¼-cup portions of dough onto the prepared sheets, leaving space between each; bake for 14–17 minutes, watching for lightly golden bottoms. Cool completely before frosting.
For the icing, mix confectioners' sugar, lemon juice, and water. Spread half the cookie with white icing and let set for 10 minutes. Stir cocoa powder into remaining icing, then spread on other half and let cookies rest until icing is firm.
Serve the cookies once the frosting sets, ensuring both vanilla and chocolate sides have distinct finishes.