Place chopped chocolate in a large glass bowl.
Combine chai powder and milk in a small saucepan. Bring to a simmer over medium heat. Remove from heat. Pour warm milk mixture over chocolate; stir until chocolate is melted and smooth. Set aside.
Combine sugar and water in a small saucepan. Cook over medium heat 6 minutes or until sugar dissolves, stirring constantly.
Beat egg yolks in a large bowl at high speed with an electric mixer 3 minutes or until pale and doubled. Gradually add sugar syrup, beating 4 minutes or until slightly thickened. Gradually fold into melted chocolate.
Beat egg whites at high speed with an electric mixer until stiff peaks form. Fold egg whites and whipping cream into chocolate mixture. Serve in mugs.
Top each serving with a dollop of sweetened whipped cream and a cinnamon stick. Sprinkle with cinnamon sugar.