Grease an ovenproof dish. Wash the apples well and remove the cores - press the corer halfway through one side of each apple. Remove the corer, turn the apple over and push the corer right through that side, then twist and take out the core. Using a sharp knife, make a cut just through the skin going completely around the widest part of the apples.
Place the apples in the dish, they should fit quite snugly, and push half the pecans into the hollows. Add the butter cubes to the hollows, then top up with the rest of the pecans and drizzle in the golden syrup. Pour 50ml water around the base of the apples and then bake in the oven for about 25 minutes, or until the apples just start to split and slightly puff up: but do not overcook. They will look and smell great.
Remove from the oven and allow to cool for about 15 - 20 minutes otherwise they will burn your mouth, I promise they will be worth the wait!
Meanwhile, heat up the custard in a pan. Serve apples in deep bowls with lashings of custard and spoon over the buttery juices from the baking dish.