Crust: Melt the butter. Mix the crums with the sugar and cacao. Add the melted butter. Stir until well mixed. Put it into a 26 cm spring-form. Press the mixture into the form. Put in refrigerator.
Filling: Melt the chocolate in a double-boiler or in micro-wave. Stir until smooth. Remove from heat. Beat the egg-whites until hard peakes form -set aside Whip the cream until soft peaks form -set aside. Whip the egg-yokes with the sugar until fluffy. Whip the cream-cheese until fluffy, add the egg-mixture and the chocolate. Stir the mixture until fully combined. Fold in the cream until combined. Finally fold in the egg-whites until combined.
Pour the mixture over the crust. Put the peca nuts on top, cover it and refrigerate for at least 6 hours, preferably overnight.