PREHEAT oven to 325º F. Grease bottom of 9-inch springform pan. Line bottom with parchment or wax paper. Grease paper.
PLACE chocolate, butter, water and coffee granules in medium, heavy-duty saucepan. Heat over medium-low heat, stirring frequently, until melted and smooth. Stir in granulated sugar until smooth. Remove from heat.
BEAT eggs in large mixer bowl for 5 minutes or until the volume doubles. Fold one-third of beaten eggs into chocolate mixture. Fold in remaining beaten eggs one-third at a time until thoroughly incorporated. Pour batter into prepared pan.
BAKE for 33 to 35 minutes or until cake has risen (center will still move and appear underbaked) and edges start to get firm and shiny. Cool completely in pan on wire rack (center will sink slightly). Cover cake; refrigerate for 4 hours or overnight. (Cake can be prepared up to 4 days in advance.)
TO SERVE: About 30 minutes before serving, remove side of pan by first running knife around edge of cake. Invert cake on sheet of parchment paper, peel off parchment pan liner, and turn the cake right-side up on serving platter. Dust with powdered sugar. Serve with dollop of sweetened whipped cream.