Add half the lemon juice and the sugar to a saucepan. Peel, core and cut the apples into thin slices. Simmer the apples in the lemon juice and sugar over a medium-high temperature until the sugar has caramelised.
Mix the elderberry juice with 150g sugar then mix. Add the apples and bring to the boil. Stir the cornflour with about 1 tablespoon cold water and mix into the soup. Bring to the boil beating vigorously with a whisk. Remove from the heat.
Semolina Dumplings: Put the butter and milk into a small saucepan and bring to the boil. Stir in the semolina and bring to the boil stirring constantly. Stir in the sugar. Remove from the heat and allow to cool a bit then add it to the hot soup using a teaspoon.