• Adjust two oven racks to divide the oven into thirds and preheat the oven to 350 degrees.
• Butter three 9-inch layer cake pans, line the bottoms with parchment or waxed paper circles, and butter the paper.
• Dust the insides of the pans all over with fine dry unseasoned bread crumbs, and tap out excess crumbs.

Prepare Bread Crumbs

• Trim crusts off any firm-textured plain day-old bread, cut the bread into 1-inch pieces and process in a food processor to make fine-textured crumbs.  Weigh 3 ounces (1 1/2 cups loosely measured) and put the crumbs into a medium size bowl.

Prepare Walnuts

• Either grind the walnuts with a manual nut grinder or process them 1/3 at a time in a food processor with 1/2 cup of the bread crumbs in each batch.  If using the food processor, pulse the nuts and crumbs with rapid on/off bursts until the nuts feel powdery and appear fluffy. Stop often to scrape the work bowl. You want the walnuts to be as fine as possible without any hint of their becoming pasty. 
• Put the nut/crumb mixture into a medium size bowl. If you’ve ground the nuts manually, put them into a medium size bowl and stir in the fresh crumbs.

Make the Torte

• Beat the yolks with the whip attachment on high speed until they are thick and lemon-colored, 3 to 5 minutes.
• While beating on medium speed, gradually add 1/2 cup of the sugar.
• Scrape the bowl, and beat on high speed about 5 minutes more, until the yolks are very thick and almost white in color and form a slowly dissolving ribbon as they fall off the beaters (NOTE: If your yolks are very yellow or orange, they will just turn a lighter shade of yellow, not white, after beating). 
• Beat in the vanilla and lemon zest.
• Scrape the yolks into a large wide bowl.
• Wash and dry the bowl and beaters.
• In the clean bowl with clean beaters, whip the whites with the salt on medium speed until the whites have thickened to the point where the beaters leave traces in the whites.
• Gradually add the remaining 1/4 cup sugar and continue beating on medium speed until the whites form stiff, shiny peaks that curl slightly at their tips. The whites should have a creamy, moist texture.
• Sprinkle about 1/4 of the nuts and bread crumbs over the yolks (you’ll see the nuts and crumbs look and feel moist) and add about 1/4 of the whites.
• Fold everything together very gently, with just a few broad strokes of the spatula, to deflate the batter as little as possible. It’s all right if streaks of white remain at this point. 
• Repeat with 3 additions of the remaining nuts and whites, folding in the last addition just until no whites show. The batter should look light and airy.
• Divide the batter evenly among the prepared pans (a kitchen scale is helpful for this step) and rotate each pan gently on the countertop to level the batter.
• Place the pans in the oven, two on the upper rack, and one on the lower rack.
• Bake for 20 to 25 minutes, until the layers are golden brown, they spring back when gently pressed, and a toothpick comes out clean.  Be careful not to overbake. Begin testing for doneness at the earlier time; the bottom layer may be baked a minute or two before the other layers. 
• Cool the cakes in their pans for 10 minutes. The cakes will settle on cooling and will be about 1 inch tall.
• Release the layers from the sides of the pan by running the tip of a sharp knife all around the edges of the cakes.
• Cover the cakes with wire racks and invert.
• Carefully lift off the pans and peel off the papers.
• Cover the layers with other racks and invert again to cool right side up.
• Cakes may be made to this point a day ahead; when completely cool, wrap layers in plastic wrap and leave them at room temperature overnight.

Make the Frosting

• To make the frosting, put the water, instant espresso, and sugar into a small, heavy saucepan.  Don’t stir.
• Set the pan over medium low heat and slowly bring the liquid to the simmer.
• Swirl the pan by its handle and cook for 2 to 3 minutes more, until the liquid is syrupy.  You should have 3 to 4 tablespoons of mocha syrup.
• Cool completely before using.
• Combine the cream with the syrup and vanilla and whip on medium high speed until the cream holds a firm shape.
• Fold in the grated chocolate.

Frost the Cake

• Line a cake plate around the edges with four strips of waxed paper in a square pattern
• Set a cake layer right side up on the plate with the edges of waxed paper just under the edges of the cake.
• Use a narrow metal spatula to spread the layer with about 1 cup of the frosting.
• Place a second layer right side up on top of the frosting and spread it with another 1 cup of frosting.
• Set the third layer right side up on top, and spread the remaining frosting around the sides and top of the cake, making the frosting on top thicker than on the sides.
• Decorate the top of the cake with candied violets or chocolate-covered coffee beans.
• Carefully remove the strips of waxed paper by pulling them towards you by a short end.
• Refrigerate for several hours before serving.

Serving and Storing

• To serve, cut portions with a sharp knife and let them warm up to room temperature before eating.

Storing

• This torte keeps well, refrigerated, for 3 to 4 days. 
• Cover the cut portion with plastic wrap applied directly to the cut cake.