Place chocolate and cream in a heatproof bowl over a pan with simmering water. Melt over low heat.
Prepare the gelatin. Dissolve gelatin in cold water and let it swell for about 5-10 minutes.
Place gelatin over low heat just until the gelatin dissolves and then pour it over melted chocolate.
In a large mixing bowl mix mascarpone with powdered sugar until combined. In another bowl whip the whipping cream until stiff peaks form. Gradually incorporate whipped cream into the mascarpone mixture.
Divide mascarpone mixture in two.
Mix half of the mascarpone mixture with melted chocolate and pour it over the bottom of the pan. Add fresh raspberries or mixed berries on top. Refrigerate for about 15-30 minutes.
Mix the other half of mascarpone mixture with berry mixture. Pour it on top of chocolate mousse.
Refrigerate for about 6 hours or overnight until set.
Before serving decorate with a ribbon, fresh berries and mint leaves.