Wipe the apples and core with an apple corer. With a pointed knife, make a slit around the middle circumference of each apple. On the top half make 5 to 6 slits down to the middle. Place the apples in a roasting tin.
Cut the marzipan into eight long sticks and insert one into each core cavity. Top with a walnut half. Brush all over with melted butter and cover with foil. Bake in the bottom of a preheated very hot oven (240°C/450°F, Gas Mark 8) for 25 minutes. Lower the oven temperature to moderate (180°C/350°F, Gas Mark 4), remove the foil and bake in the centre of the oven for a further 30 to 40 minutes or until soft but not floppy. Serve with Butterscotch sauce and pouring cream.