Preheat the oven to 200°C/fan 180°C/gas mark 6. Clean the potatoes, then prick all over with a fork. Microwave on high for 10 minutes, then turn them over and heat for a further 10 minutes. Test with a sharp knife to check the potato has cooked through.
Carefully remove the potatoes from the microwave and let them cool slightly before cutting a little under a third off the top. Scoop out the centre using a spoon, making sure you keep the skin in tact. It should be a like potato shell with approximately 1cm of potato left.
Place the scooped potato into a bowl. Add the milk, butter and 100g cheese and season well. Add the nutmeg and mash well until smooth. Set aside.
Heat the olive oil in a large frying pan over a medium heat. Add the onion, carrot and celery and sauté for 8-10 minutes until softened. Add the garlic, tomato purée, thyme and oregano and cook for a further 1 minute. Add the quinoa bolognese, then fill the tub halfway with water. Add to the pan with the bay leaf, then stir and bring to a boil. Cover, lower the heat and simmer for 5 minutes.
Fill each potato with the quinoa mixture. Push down lightly to pack it in. Pile some of the mashed potato on to each potato, then sprinkle over the remaining cheese. Place them on a tray, then transfer to the oven and bake for 20 minutes until the top of each potato is golden brown. Serve, sprinkled with the parsley.