Peel the potatoes, wash them, quarter them and cook covered in salted boiling water for 20 minutes.
Heat the milk, butter, a little salt, pepper and nutmeg. Cut 3/4 of the chives into fine rolls.
Drain the potatoes and let them evaporate. Press the cooled potatoes through a potato press or mash them finely. Gradually stir in the hot milk mixture with a wooden spoon. Season with salt, pepper and nutmeg. Fold in the chives rolls and fried onions.
Spread the puree into a form approx. 30 cm long. Make 6 hollows with the back of a wet spoon, beat in the eggs and sprinkle with cheese.
Bake in the preheated oven at 200 ° C on the 2nd rack from the bottom for 22-25 minutes (convection is not suitable).
Cut the remaining chives into rolls, mix with a little salt and pepper and spread on the casserole.