Preheat oven to 350F. Coat a 9-inch springform pan with cooking spray and cocoa; shake off excess cocoa.
Place butter in large bowl; beat until smooth. Add 1 cup sugar; beat until creamy. Add almonds, chocolate and egg yolks; beat thoroughly with a mixer at medium speed. Set aside.
Beat egg whites with a mixer at high speed until soft peaks form (do not overbeat). Stir one-third of egg whites into chocolate mixture; gently fold in remaining egg whites.
Scrape batter into prepared pan. Bake 35 to 40 minutes or until a wooden pick inserted in center comes out almost clean. Cool 30 minutes in pan on wire rack. Release sides of pan and slide onto a serving plate.