In a medium mixing bowl, whisk the yolks with the vanilla extract. Whisk in half the sugar and continue to beat until very light and frothy, about 5 minutes. Combine the flour and cornstarch and sift once to aerate. In a clean, dry bowl, beat the egg whites with the salt until they hold a very soft peak. Beating faster, add the remaining sugar in a very slow stream, beating until the egg whites hold a firm peak. Fold the yolks into the whites. Sift the flour and cornstarch over the eggs in 3 additions, folding them in gradually. Do not over-mix the batter. Pour the batter into a buttered and paper-lined 9- or 10-inch round pan, 2-inches deep and smooth the top. Bake the Pan di Spagna at 350 degrees, 30 to 40 minutes, until it is well risen and feels firm when pressed gently with the palm of the hand. Immediately loosen the layer from the side of the pan with a small knife or spatula. Invert the layer and leave the paper stuck to it. Turn the layer right side up and cool it on a rack. Double-wrap the layer in plastic and keep it in the refrigerator up to 5 days or freeze it. Variations: Flavor the batter with a grated orange or lemon zest or a tablespoon of Anisette.
For the chocolate filling, bring the cream to a boil and remove the heat. Add finely cut chocolate, stir once and let stand for 3 minutes. Whisk smooth, pour into a bowl and cool until set, several hours at a cool room temperature. Set aside. For the syrup, bring sugar and water to a boil in a small pan. Cool and stir in Maraschino. For the pistachios, place in a pan and cover with water. Bring to a boil, drain and rub in a towel to loosen skins. Go over pistachios to separate from skins. Place pistachios on a jelly roll pan and dry out at 325 degrees about 5 minutes. Cool and chop coarsely. To prepare the layers, cut the Pan di Spagna into 5 thin horizontal slices. Reserve 2 of the slices, then cut the other slices into smaller disks, each 1-inch smaller in diameter then the reserved 2, to make a 9, 8-, and 7-inch disk. Reserve scraps. To finish the filling, beat the butter by machine until soft and light, then beat in the cooled chocolate mixture all at once. Beat again until light, then beat in the Maraschino. Stir in half of the chopped pistachios. To assemble, place one of the 10-inch layers on a platter or cardboard and moisten with the syrup. Spread the filling. Continue with the remaining layers. After spreading the 7-inch layer with the filling, form a 6-inch layer with the scraps on top of it. Moisten the 6-inch layer and spread the entire outside of the cake with the filling. Cut a slash from the center to the edge of the reserved 10-inch layer and cover the entire outside of the cake with it. Moisten with the remaining syrup and spread with the remaining filling. Press the reserved pistachios all over the outside of the cake. Dust lightly with the confectioners' sugar.
Recipe courtesy of Nick Malgieri, Director Baking Program, Peter Kump's Cooking School