In a bowl, add in the chocolate and set aside. Whip 500 ml of cream until it becomes a nice whip cream. Becareful not to over beat. While the cream is whipping up, in a saucepan, add the other 500 ml of heavy cream and bring to boil. Once it is boiled, pour over chocolate. Let cool for about 2 mins. Stir chocolate with cream until you get a nice smooth chocolate surface. Should be about 30 secs or so. Now fold in the whip cream until you see that both the cream and chocolate are smooth. Place in refrigerator for about an hour. Depending on the thickness of the whip cream, it may take more than an hour to take and become a delicious chocolate mousse.