Heat oven to 350 degrees. Butter bottom and side of 9 inch round pan (or springform pan). Line with waxed paper and grease paper. Shake in flour.
Break amaretti biscuits in blender to equal 1/3 cup (approximately 5 or 6 biscuits).
Melt chocolate with water in double boiler. Stir occasionally until smooth. Remove from heat. Cool.
Beat 1 cup of butter until creamy. Add sugar until well blended. Beat in yolks one at a time. Alternate adding flour with cookie crumbs (1/2 at a time). beat well. Fold in chocolate.
Beat egg whites until stiff. Fold into batter.
Pour batter into prepared pan. Bake until toothpick inserted in center comes out clean (40-45 minutes). Cool on wire rack 10 minutes. Invert to serving platter. Peel paper. Cool completely. Sprinkle with powdered sugar. Top with whipped cream. Serves 8.
