Wash the potatoes and boil in water for about 20 minutes. Meanwhile clean, wash and cut leek into rings. Peel, wash and dice the carrots. Cook in boiling salted water for about 5 minutes.
After about 3 minutes add leek. Drain vegetables and rinse with cold water. Peel onion and chop finely. Knead with minced meat, egg, breadcrumbs, salt, pepper and some chilli powder. Form about 8 meatballs with wet hands.
Heat clarified butter in a frying pan. Fry meatballs in it from all sides for about 4 minutes. Drain potatoes, rinse with cold water, peel and slice. Heat crème fraîche and 1/4 litre water.
Dissolve the bouillon in it. Melt the processed cheese preparation in the sauce while stirring. Remove from heat, stir in the egg yolk. Season to taste with nutmeg. Grease a casserole dish. Layer potato slices, carrots and leek, pouring a little sauce over each layer.
Put meatballs on top. Spread slices of processed cheese on the casserole. Bake the casserole in a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: level 4) for approx. 30 minutes. Garnish with chives.