Preparation Preheat oven to 350°F. Butter 9-inch-diameter springform pan with 2 3/4-inch- high sides. Combine chocolate, almonds and 1 cup sugar in processor. Process until all ingredients are very finely chopped and mixture appears grainy. Using electric mixer, beat yolks and vanilla in large bowl until pale yellow and thickened, about 3 minutes. Add chocolate mixture to yolk mixture and fold together (mixture will be very thick). Using mixer fitted with clean beaters, beat egg whites and cream of tartar in another large bowl to stiff peaks. Fold whites into batter in 3 additions. Pour batter into cake pan. Bake until top is golden and tester inserted into center comes out clean, about 45 minutes. Transfer cake to rack and cool. (Can be made 1 day ahead. Cover and let stand at room temperature.) Run knife around pan sides to loosen cake. Release pan sides. Transfer cake to platter. Sift powdered sugar over cake. Top with chocolate curls, if desired. Serve with ice cream.
Preparation Preheat oven to 350°F. Butter 9-inch-diameter springform pan with 2 3/4-inch- high sides. Combine chocolate, almonds and 1 cup sugar in processor. Process until all ingredients are very finely chopped and mixture appears grainy. Using electric mixer, beat yolks and vanilla in large bowl until pale yellow and thickened, about 3 minutes. Add chocolate mixture to yolk mixture and fold together (mixture will be very thick). Using mixer fitted with clean beaters, beat egg whites and cream of tartar in another large bowl to stiff peaks. Fold whites into batter in 3 additions. Pour batter into cake pan. Bake until top is golden and tester inserted into center comes out clean, about 45 minutes. Transfer cake to rack and cool. (Can be made 1 day ahead. Cover and let stand at room temperature.) Run knife around pan sides to loosen cake. Release pan sides. Transfer cake to platter. Sift powdered sugar over cake. Top with chocolate curls, if desired. Serve with ice cream.