Bring the apple juice to the boil in the saucepan and reduce to approx. 300 ml. Peel shallots and cut into large pieces with the peeled and cored apple. Heat the butter, add the shallot and apple pieces and sauté for 5 minutes. Add the curry and the scraped-out vanilla pod and cook for about 1 minute. Pour the stock, reduced juice and cream, bring to the boil and cook over medium heat for 5 minutes, stirring occasionally.
Finely puree the soup, strain through a fine sieve, bring to the boil again. Thicken lightly with a little cornstarch. Add soy sauce and vanilla pulp. Froth the milk. Pour soup into hot cups and put on the milk foam just before serving.
Place the soup bowl on a large dinner plate and put 2 baked king prawns on the skewers or on top.