For our matzoballs, whipped egg whites provide a light,airy texture, while chicken fat lends a velvety softness and complex flavor.
Whisk yolks, fat, 1/2 cup stock, and the salt in a medium bowl; season with pepper. Stir in matzo meal and parsley.
Put egg whites into the bowl of an electric mixer fitted with the whisk attachment. Beat on medium-high speed until stiff peaks form. Add to matzo mixture; whisk until smooth. Refrigerate until slightly thickened, about 30 minutes.
Bring remaining stock to a boil in a large pot. Scoop out 1 1/2-inch balls of the matzo mixture, and add to stock. Reduce heat. Cover, and simmer until matzo balls are slightly firm and cooked through, about 15 minutes. Garnish with dill.