Peel, wash and quarter the potatoes and cook in boiling salted water for about 20 minutes. Boil the eggs in boiling water for about 8 minutes until soft. Peel and finely dice onion. Melt the fat, fry the onion in it.
Sweat flour in it. Add 1/4 litre of milk and stock while stirring, bring to the boil. Add peas and simmer for about 5 minutes. Drain eggs, quench and peel. Drain and mash potatoes and stir in 1/8 litre milk.
Season to taste with salt and nutmeg. Arrange mashed potatoes, eggs and pea sauce on plates, garnish with parsley.