Mix the raisins with the rum and jam, and let steep for 30 min. Peel the apples and remove the core with an apple corer.
In a pot, bring the water, white wine, sugar, juice and zest from the lemon, cinnamon stick, and cloves to a boil over medium-high heat. Reduce to low heat and stew the apples in this mixture for 15 min until they are still firm to the bite. Remove the apples and place each into a dessert bowl. Fill the center of each apple with the raisin-jam mixture and top with roughly sliced almonds.
In a small bowl, stir the custard powder with some of the milk until smooth. In a pot, bring 300 ml of the apple-wine cooking liquid to a boil over medium heat with the remaining milk. Stir in the custard powder mixture and simmer for 2 min while stirring constantly. Pour this custard over the apples in the bowls, sprinkle with the chopped walnuts, and drizzle with chocolate sauce. Serve warm with whipped cream.