Preheat oven to 180°C (350°F). Cut apples in half through the stem and scoop out core.
Combine sugar, pecans, sultanas, and cinnamon in a small dish and set aside.
Place one apple half, cut-side down, on a chopping board. Position one chopstick on the board above the apple, and another below. Carefully cut apple into 1/2 cm slices – your knife will hit the chopsticks and stop you from slicing all the way through. Repeat with remaining halves.
Arrange sliced apple halves in a baking dish. Add water to base of pan. Sprinkle over nut mixture and drizzle with oil or butter.
Cover dish tightly with foil and bake 30 minutes. Uncover, baste apples with pan juices, and bake a further 10 minutes until tender and golden.
Serve hot or at room temperature. The apples are delicious on their own, but make a perfect accompaniment for yoghurt, ice cream, porridge, or even roast dinner.
You can use a mix of apples but some varieties (such as Fuji, Pink Lady and Jazz) hold their shape better as they cook.