Grease a 9-inch springform pan; line bottom with parchment paper. Grease paper; dust with flour. Set aside. In a small heavy saucepan combine butter and chocolate. Stir over low heat till melted and smooth; set aside.
Place eggs and sugar in a blender container or food processor bowl. Cover and blend or process until smooth. Add nuts. Blend or process about 1 minute or until nearly smooth. Add melted chocolate mixture, cocoa powder, and liqueur; blend or process just until combined. Spread batter evenly in the prepared pan.
Bake in a 350 degrees F oven for 35 to 40 minutes or until sides are puffed and set about 2 inches in from edge of pan. Place cake on a wire rack; cool thoroughly. Loosen sides of cake; remove sides of pan. Invert cake onto rack. Remove parchment paper. Place rack with cake on baking sheet. Pour warm Mocha Glaze over cake, covering top and sides.
Pour melted baking bar into a plastic storage bag. Snip one corner of the bag to make a small opening. Starting at center of cake, pipe a spiral to the outer edge. Draw 8 to 10 lines with a toothpick from center of cake to edge at regular intervals to achieve a spider web effect. If necessary, chill cake until glaze is partially set but still sticky (5 to 10 minutes). Press nuts onto sides of cake. Transfer cake to plate and refrigerate. Makes 12 to 16 servings.
In a medium heavy saucepan heat 3 tablespoons butter and 1 tablespoon light-colored corn syrup over low heat, stirring occasionally until butter melts. Add one 6-ounce package (1 cup) semisweet chocolate pieces; stir till melted and smooth. Remove from heat. Add 3 tablespoons butter and 2 tablespoons coffee liqueur or strong coffee; whisk until smooth.