Preheat oven to 170 C (fan-forced). Using an apple corer remove the core from each apple. Use a small sharp knife to trim around top and base of apple so the hole is about 2-2 1/2cm wide.
Put the oats, raisins, sugar, walnuts and cinnamon in a small bowl. Mix well. Add the spread and the apple juice. Mix until well combined.
Place the apples in a small ovenproof dish. Spoon the filling evenly into the centre of each apple. Pour the water around the base of the apples. Cover dish with foil and bake for 30 minutes or until the apples are almost tender.
Remove the foil and cook for a further 10-15 minutes or until the apples are very tender. Drizzle 1 1/2 tablespoons of custard over each apple, to serve.