Hungarian Chocolate-Walnut Torte

Ingredients:
3/4 cup sugar (if using half semisweet and half sweet chocolate) or 3/4 cup plus 2 tablespoons sugar (if using all semisweet chocolate)
"6 ounces fine-quality chocolate, preferably half dark sweet (sometimes labeled Germans Sweet Chocolate), and half semisweet, but all semisweet is also delicious; cut into small pieces", 6 large eggs, separated
6 ounces shelled walnuts (1 3/4 to 2 cups)
3 tablespoons matzoh meal
"Optional accompaniments: Passover Confectioners Sugar (recipe below) or Chocolate Icing (recipe below); heavy cream, freshly whipped to soft drifts and barely or very lightly sweetened; or vanilla ice cream", Optional garnish: walnut halves
6 tablespoons (3/4 stick) unsalted butter or margarine
6 ounces fine-quality semisweet or bittersweet chocolate
cut into small pieces

Instructions:
Have all ingredients at room temperature.
Line the bottom of an 8-inch square cake pan or a 9-inch springform pan with parchment or wax paper.
Preheat the oven to 350°F.
In a heavy-bottomed 2-or 3-quart saucepan, combine 1/2 cup of the sugar and 1/2 cup water and bring to a boil, stirring constantly over medium heat. Continue boiling and stirring until all the grains of sugar have completely dissolved and the mixture forms a simple syrup. Remove the pan from the heat and stir in the chocolate until melted and smooth. Set aside to cool.
In a large bowl, beat the egg yolks with an electric mixer until light and thickened, about 4 minutes. Grind the walnuts with the remaining sugar and the matzoh meal in a food processor using the pulse motion and stir into the egg yolks. Add the cooled chocolate mixture and combine thoroughly.
Using clean beaters, beat the egg whites in another bowl until they hold stiff peaks. Gradually fold the whites into the chocolate-walnut mixture, incorporating them gently but thoroughly so that no whites are visible. Pour the batter into the prepared pan and bake for 30 to 40 minutes, until puffed and almost set but still a little gooey in the center. A wooden toothpick inserted 1 inch from the edge should come out clean.
Remove the pan from the oven and let cool on a rack. When completely cool, unmold the cake by running a thin-bladed knife around the edges of the cake to release it from the pan (or release the springform); invert onto a platter. Peel off the parchment paper. Serve the torte at room temperature.
If desired, lightly dust with Passover confectioners' sugar. For a lovely, simple presentation, place a doily or a stencil—handmade by you or, even better, your children—over the torte, then sprinkle with the sugar. Carefully remove the doily or stencil.
Or glaze with the chocolate icing. Lay long strips of wax paper or foil on a cake plate or serving platter and place the cake on top. Pour the glaze over the top of the cake, letting it drip down the sides. Using a spatula, evenly spread the glaze over the top and sides. Now, pull out and discard the paper strips or foil strips--the plate will be clean and ready for serving. If you'd like, garnish with a few walnut halves attractively placed in the center of the cake. Refrigerate the cake for about an hour to set the glaze, but bring it to room temperature before serving.
The plain or frosted torte is heavenly with generous dollops of whipped cream or vanilla ice cream.
In a blender, mini-food processor, or clean coffee grinder, whirl 1 cup minus 1/2 tablespoon regular granulated sugar until it is powdery. Place in a small bowl and stir in 1/2 teaspoon potato starch. Sift before using. (Recently commercial Passover confectioners' sugar, made without cornstarch, has appeared in some stores with large kosher-for-Passover sections. If available, by all means use it here.)
Melt the butter or margarine slowly in a heavy saucepan over very low heat. When half is melted, gradually whisk in the chocolate, stirring well as it melts. After all the chocolate has been added, stir in 2 tablespoons water and beat well until the glaze is completely smooth. Let the mixture cool about 5 minutes to thicken slightly.