Bring all ingredients, especially eggs and sour cream, to room temperature before mixing to ensure a smooth, emulsified batter that creates the signature ultra-moist crumb texture.

Don't skip the sour cream—it adds tanginess and moisture that keeps these cookies impossibly soft for days, while also tenderizing the crumb structure for that authentic New York bakery texture.

Warm your icing slightly and test consistency on a cooled cookie before coating; it should flow smoothly to create a thin, glossy finish that sets perfectly without cracking or pooling.

Dip one half of each cookie into vanilla icing first, let it set for 5 minutes, then dip the other half into chocolate icing to prevent colors from bleeding and creating a crisp division line.

Use both baking soda and baking powder together as specified—the soda reacts with the sour cream for immediate rise and browning, while the powder ensures even lift throughout the cookie for that perfect cakey structure.