Preheat oven to 350 degrees F.
Combine matzo meal and walnuts in a food processor; process until nuts are finely chopped. Spread on a baking sheet and toast until fragrant, 5 to 10 minutes. Let cool.
Whisk eggs, 3/4 cup sugar and vanilla in a large bowl until blended. Stir in the matzo mixture, apple, cocoa and chocolate.
Beat egg whites and salt in large, clean bowl, with an electric mixer on medium speed until frothy. Increase speed to high and beat until soft peaks form. Add remaining 1/2 cup sugar 1 tablespoons at a time, beating until glossy and stiff peaks form.
Stir one-quarter of the beaten whites into the batter. Gently fold in remaining whites with a rubber spatula. Scrape the batter into an ungreased 9-inch springform pan, spreading evenly. Tap pan lightly on counter to release air bubbles.
Bake torte until top springs back when touched lightly and a skewer inserted in the center comes out clean, 40 to 45 minutes. With a knife, loosen edges of torte. Let cool in pan on a wire rack. (Torte will sink in center).
Remove pan sides and place torte on a serving platter. Dust with confectioners' sugar and serve.