Chill cream. Pour the whipping cream into a metal mixing bowl and place in the refrigerator.
Prepare sugar syrup. Place the sugar with 2 tablespoons of water in a small saucepan. Place on medium heat and bring to a boil. Boil for two minutes or until 120° C (248° F).
Whisk eggs and syrup. Break the eggs into a mixing bowl and begin beating them with an electric whisk. Continue beating and pour in the sugar syrup in a very thin steady stream. Beat in the coffee extract. Continue beating until the mixture has completely cooled and has become very thick and ribbony (about 10 minutes).
Whip cream. Remove the mixing bowl from the refrigerator and whip the cream until soft peaks form. Whip in the vanilla sugar and continue beating until firm.
Fold together. Fold the whipped cream delicately into the whipped egg mixture. Fold in the ground praline and continue folding just until everything is mixed. Spoon this mixture carefully into 6 parfait glasses.
Layer if you wish. Alternatively you can reserve some of the ground praline and layer it with the egg and cream mixture in the parfait glasses.
Freeze. Cover the glasses with plastic wrap and place in the freezer for 4 hours before serving.