Preheat oven to 350 degrees.
Generously butter and flour 9-inch springform pan.
Melt chocolate in top of double boiler over simmering water, stirring chocolate until smooth.
Remove chocolate from over water.
Cool chocolate 10 minutes. Beat 3/4 cup sugar, butter and vanilla extract to blend.
Add egg yolks 1 at a time, beating well after each addition. Add melted chocolate; beat until just combined. Mix in poppy seeds.
Beat egg whites until stiff but not dry.
Fold half of beaten egg whites into chocolate mixture.
Fold flour into remaining beaten whites. Fold egg white mixture into chocolate mixture.
Pour batter into prepared pan. Spread to level.
Bake until tester inserted in center of torte comes out clean, about 45 minutes. Transfer pan to rack and cool completely.
Remove pan sides.
Sift powdered sugar over torte. Serve with whipped cream.