Cut open the vanilla pod and scrape out the pulp. Put the vanilla pod, pulp, sugar and cream in a saucepan, mix, bring to the boil and let stand for 10 minutes. Take out the vanilla pod. Whisk the egg yolks and use the whisk to work them into the cream. Heat the mass slowly to just before the boiling point and beat vigorously with the whisk until it begins to become thick. Let the vanilla sauce cool down while stirring repeatedly. Then put in the refrigerator. (Don`t panic if the sauce isn`t particularly thick - it will still be in the fridge.) Goes particularly well with the apple puff pastry tartlets!