Preheat the slow cooker on the high setting.

Start by grating the zest of the orange.

Use some of the butter to grease the bottom and sides of the slow cooker with a pastry brush.

Place the pudding rice, orange zest, cocoa powder, sugar and remaining butter in the bottom of the cooker.

Add the milk and evaporated milk and stir to combine.

Place the lid on the slow cooker and cook for four hours.

Stir the mixture each hour to ensure that it does not stick to the bottom of the slow cooker. This will ensure that the starch is evenly distributed, and the mixture will become thick and creamy.

To serve, this chocolate rice pudding is delicious with some chocolate grated over the top.