"The thing about eating the Black and White cookie, Elaine, is you want to get some black and some white in each bite. Nothing mixes better than vanilla and chocolate And yet somehow racial harmony eludes us. If people would only look to the cookie all our problems would be solved." - Jerry Seinfeld, Seinfeld (The Dinner Party)

Black and white cookies are one of the representative foods of New York City. They are huge, soft, frosted and tasty. In fact, while they have been at bakeries in the Big Apple for decades, it is only recently that they have spread widely beyond the city limits. The black and white cookie is actually more like a cupcake than a cookie, as it has a very soft and cakelike texture and is frosted. Some people frost butter or sugar cookies and disguise them as black and whites, but, to be honest, this is wrong. I'm sure they taste fine, but they are not black and whites.
A black and white should consist of a cookie/circle of cake (like the top of a cupcake) that has a hint of lemon flavor. The icing, while always half black and half white, can be a variety of things. You can use a regular frosting (boiled or buttercream), thinly spread, or a smoother ganache type frosting, but probably the most common frosting is a simple sugar one. Conveniently, it is also the easiest. Only lightly flavored with chocolate or vanilla, the sugary icing dries firm on the cookies and adds a nice layer of sweetness.
I believe that, traditionally, the flat part of the cookie is frosted, to provide an even surface, and the cookie is set on the rounded side. I like to frost the rounded part because not only do you get more frosting, but I prefer the way the cookies lie on the plate.
This recipe is adapted from Cooking Light, as black and whites are not usually very waistline friendly, due in large part to their huge size. These cookies are more managable and come out to be 3 in/8cm in diameter. Even when cooled completely, the tops of the cookies felt sticky and I was worried about their low fat content. Once they were frosted, though, they were fine. The cookies tasted great and stayed nice and moist!

Black and White Cookies
adapted from cooking light

Cookies:
1 1/2 cups ap flour
1 1/2 tsp baking powder
1/2 tsp salt
2/3 cup unsweetened applesauce
1 cup sugar
1/4 cup butter, softened
1 tsp vanilla extract

1 tsp lemon juice or a few drops of lemon oil
2 large egg whites

Icing:
1 1/2 cups confectioners sugar, divided
3 tbsp milk or light cream, divided
1/4 teaspoon almond extract
1/2 tsp vanilla extract
2 tablespoons unsweetened cocoa