4 oz semisweet chocolate, chopped
2 cups whole blanched almonds
3/4 cup sugar
8 large egg whites (4 in each of two bowls)
1 teaspoon grated orange rind

Lightly grease an 8 inch springform pan. Line base and side of pan with parchment paper or wax paper. Generously grease liner. Melt chocolate in a medium bowl over a pan of nearly simmering water. Stir until smooth. Remove bowl of chocolate from water; let cool. Grind almonds with 2 Tablespoons sugar in a food processor to a fine powder. Add 2 egg whites (half those in one bowl) and 1/4 cup sugar; process 10 seconds or until smooth. Add another 2 egg whites and 1/4 cup sugar; process again. Transfer to a medium bowl. Stir in orange rind. Beat remaining egg whites in a large clean bowl until soft peaks form. Gradually beat in remaining 2 Tablespoons of sugar. Beat at high speed until whites are stiff and shiny, but not dry. Slowly stir cooled chocolate into almond mixture. Gently fold about 1/4 of whites into chocolate mixture until nearly blended. Fold in remaining whites in 3 batches. Chocolate mixture will not mix easily with whites, so continue folding until batter is blended. Spread batter in prepared pan. Bake about 40 minutes or until cake springs back when pressed lightly. Cool in pan on a rack 5 minutes. Invert cake onto rack. Gently release spring and remove sides and base of pan. Carefully peel off liner. Cool cake completely. Turn cake onto another rack, then onto a platter so smooth side of cake faces up. Serve at room temperature.