Wash the raisins in hot water, drain and soak in the rum. Wash apples, quarter them, remove seeds and cut them into slices. Separate eggs. Beat egg whites and a pinch of salt until stiff. Whisk egg yolk and milk. Stir in flour, 50 g sugar and sour cream. Fold in 2 portions of beaten egg white.
Sprinkle an ovenproof pan (26 cm Ø) with 1 tablespoon of sugar. Place the apple slices in a circle in the pan. Spread 2 tablespoons of butter in flakes on top. Heat until the butter has melted. Pour the dough evenly over the apples. Drain the raisins, catch the rum and sprinkle the raisins on the dough. Bake for about 2 minutes. Then bake in a preheated oven (electric cooker: 200 °C/circulating air: 180 °C/gas: see manufacturer) for 10-15 minutes until golden brown.
Melt 1 tablespoon of butter in flakes on the edge of the pan until the pancake separates from the edge of the pan. Drizzle collected rum over the pancake. Flip the pancakes over. Dust with icing sugar.