Preheat oven to 150°C (300°F) and place rack in the center.

Grease a 10x10 inch square baking dish with butter.

Dice whole wheat brown bread into bite-sized pieces.

Place the bread cubes into the greased baking dish.

Sprinkle chopped walnuts, apples, and raisins over the bread cubes.

In a large bowl, whisk eggs and caster sugar on high speed until thick and fluffy.

Beat in vanilla extract, ground cinnamon, melted butter, and milk until well combined and fluffy.

Pour the prepared custard over the bread cubes, ensuring they are completely covered.

Press down the bread cubes with a fork to ensure the custard seeps into the crevices.

Place the bread pudding dish on a roasting pan.

Pour hot water into the roasting pan so that the water is halfway up the sides of the baking pan.

Bake for about 45 minutes, or until a toothpick inserted in the center comes out clean.

Cool slightly before serving.

Serve warm or cold.