Place millet in a strainer and rinse under cold running water. Transfer into a pot, and pour in the milk. Bring to a boil. Reduce heat to low, cover with lid and simmer for 15 minutes.
Transfer the cooked millet into a high-speed blender or food processor. Add the raspberries and protein powder. Blitz until smooth and creamy. If the pudding is too thick, you can add more milk. Serve with additional raspberries and maple syrup (optional).