This cake batter is made with two eggs, two yolks, brown sugar (no white sugar) and buttermilk, ingredients that give the cake an incredible rich flavor and beautiful texture. The other key is that the recipe calls for mini chocolate chips. As Pisano says, "It's imperative that you use mini chocolate chips. The big ones will sink, even if you coat them with flour, too heavy even for this batter. This cake works because the batter is thick enough to hold up those lightweight, little chips."