Mix the cream with sugar, agar agar, cornstarch and vanilla sugar in a saucepan well with a whisk. Bring to the boil and simmer for about 2 minutes over low heat while stirring. Take the pot off the stove and pour the contents into cold rinsed molds.
Chill for at least 3 hours.
Before serving, carefully loosen the edge with a knife and turn the panna cotta onto a plate.
If desired with fruit sauce, e.g. Garnish with pureed strawberries or fresh fruit.