Preheat oven to 350°F (175°C).
Grease springform pan with butter thoroughly.
Melt chocolate and butter using double boiler.
Beat eggs and sugar until light and fluffy.
Fold melted chocolate mixture into egg mixture gently.
Pour batter into prepared springform pan evenly.
Bake for 20-25 minutes until set completely.
Cool cake completely in pan before removing.
Puree raspberries and strain to remove all seeds.
Dissolve gelatin in warm water for 5 minutes.
Whip cream to soft peaks with powdered sugar.
Combine raspberry puree with dissolved gelatin mixture.
Fold whipped cream into raspberry mixture very gently.
Spread mousse over cooled chocolate base evenly.
Refrigerate cake for minimum 3 hours until firm.
Garnish with fresh raspberries and chocolate shavings.