Peel, wash and chop the potatoes and cook in boiling salted water for about 20 minutes until soft. In the meantime peel and halve onions and cut them into slices or half rings. Heat 2 tablespoons of oil in a frying pan.
Fry the onions for about 10 minutes, stirring occasionally. Sprinkle sugar over it, stir in and let it caramelize. Add 100 ml water and soy sauce and simmer for 5-8 minutes.
Heat 1 tablespoon of oil in a frying pan. Fry the sausages for about 5 minutes, turning them over. Drain the potatoes. Add milk and butter to the potatoes and mash to puree. Season to taste with salt, pepper and nutmeg.
Divide the puree, sausages and onions into 4 ovenproof tins and bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: see manufacturer) for approx. 15 minutes. Wash parsley, shake dry, pluck leaves from the stalks and chop finely.
Sprinkle parsley over the puree.