Combine sliced berries, sugar, and one tbsp rum or 1 tsp rum ext. in a medium bowl. Combine remaining rum or ext. and orange juicein a small measuring cup. Melt chocolate slowly over hot water in double boiler or small bowl. Stir occasionally. Cool to room temp. Beat whipping cream and cooled chocolate until soft peaks form. Slice angel cake horizontally into three layers.
Place one layer on large cake plate. Drizzle with 1/3 of oranje juice mix. Top with 1/3 of cream chocolate mixture and 1/2 of the sliced berries. Repeat layers, ending with cream spooned over top of cake and partially down sides. Garnish with whole berries and mint leaves. Refrigerate one to two hours. To serve, cut into 8 wedges.