Peel, wash and quarter the potatoes. Cook in boiling salted water for about 20 minutes. Cook eggs in boiling water for about 10 minutes, rinse with cold water, peel and halve. Clean, wash, drain and chop the rocket.
Set some leaves aside for garnishing. Melt 2 tablespoons of fat in a large pot. Stir in the flour and sweat. Deglaze with stock and 450 ml milk, bring to the boil and simmer for 1-2 minutes, stirring.
Stir in mustard, season with salt, pepper, sugar and lemon juice. Add the eggs to the sauce and warm them up. Stir in the rocket except for something to sprinkle. Drain potato water. Add 200 ml milk and 2 tbsp fat to the potatoes and mash to puree.
Season with salt, pepper and a little nutmeg. Arrange everything, sprinkle with rocket and garnish.