From 1922:
Fill a deep baking dish with a layer of sliced apples, sugar and well washed prunes, heaping the fruit well up in the centre.
Cover with pastry, brush over with beaten egg or milk, mash with a knife, and bake in a moderately hot oven for ¾ of an hour or until the juice boils out of the fruit.
Sprinkle over with sugar and serve while hot or cold.