Clean and wash the leek and cut into fine rings. Peel, wash and thinly slice the carrots. Peel, wash and roughly grate the celery. Peel, wash and finely grate parsley root.
Peel garlic and dice finely. Heat 2 tablespoons of oil in a frying pan. Add garlic and vegetables and steam for about 8 minutes, turning. Season with salt and pepper. Place in a sieve, drain well and allow to cool.
Beat the eggs. Season well with salt, pepper and nutmeg. Mix drained vegetables and eggs. Heat 2 tablespoons of oil in a pan (26 cm Ø). Add the egg and vegetable mixture. Cover and allow to set for 15-20 minutes over a low to medium heat.
In the meantime, wash the chives, shake them dry and cut them into fine rolls. Mix yoghurt and chives, up to 1 teaspoon for garnishing. Season to taste with salt and pepper. Carefully remove the frittata from the bottom of the pan with a spatula, slide it onto a plate and cut into pieces.
Arrange the frittata with diced ham and yoghurt garnished with chives. Add the remaining ham cubes and yoghurt.