Making Almond Powder: Combine the almonds, the 2-1/2 tablespoons confectioner's sugar and the 1/4 cup cocoa in a food processor fitted with the steel blade. Process until the almonds are a fine powder.
Blending the Batter: Butter the bottom and sides of an 8-inch springform pan with the 1 tablespoon of butter. Cut a circle of parchment paper to cover the bottom of the pan. Butter the paper with 1/2 tablespoon butter and line the pan with it, butter side up. Use the 3 to 4 tablespoons flour to coat the entire interior of the springform, shaking out any excess. Preheat the oven to 375 F, and set a rack in the center of the oven. Using an electric mixer fitted with the paddle attachment or a hand-held electric mixer, beat the butter and sugar at medium speed 8 to 10 minutes, or until almost white and very fluffy. Scrape down the sides of the bowl several times during beating. Beating the butter and sugar to absolute airiness ensures the torta's fine grain and melting lightness. Still at medium speed, beat in the peanut butter. Then beat in the egg yolks, two at a time, until smooth. Reduce the speed to medium-low, and beat in the melted chocolates, the dissolved coffee, and the rum and vanilla. Then use a big spatula to fold in the almond powder by hand, keeping the batter light.
Whip the egg white to stiff peaks. Lighten the chocolate batter by folding a quarter of the whites into it. Then fold in the rest, keeping the mixture light but without leaving any streaks of white.
Baking: Turn the batter into the baking pan, gently smoothing the top. Bake 15 minutes. Then reduce the oven heat to 325 F and bake another 15 to 20 minutes, or until a tester inserted in the center of the cake comes out with a few streaks of thick batter. The cake will have puffed about two thirds of the way up the sides of the pan. Cool the cake 10 minutes in the pan set on a rack. The cake will settle slightly but will remain level. Spread a kitchen towel on a large plate, and turn the cake out onto it. Peel off the parchment paper and cool the cake completely. Then place a round cake plate on top of the cake and hold the two plates together as you flip them over so the torta is right side up on the cake plate.
Serving: Torta Barozzi is moist and fudgy. Just before serving, sift the tablespoon of cocoa over the cake. Then top it with a sifting of the confectioner's sugar. (Or for a whimsical decoration, cut a large stencil of the letter "B" out of stiff paper or cardboard. Set it in the center of the cake before dusting the entire top with the confectioner's sugar. Carefully lift off the stencil once the sugar has settled.) Serve the Barozzi at room temperature, slicing it in small wedges.
Wine Suggestion: In Vignola, homemade walnut liqueur (Nocino) is sipped with the Barozzi. Here, the black muscat-based Elysium dessert wine from California does well with the cake's intense chocolate.