Wash the potatoes, boil in plenty of water and cook over medium heat for about 15 minutes. In the meantime peel, wash and slice the carrots. Cook the carrots in boiling salted water for about 5 minutes.
Drain and let drain. Clean, wash and cut the leek into pieces. Peel garlic and chop finely. Heat the oil in a frying pan, fry the leek and garlic on a low heat for about 10 minutes.
Add the mince and fry over a high heat. Add tomato paste and dried herbs, season with salt, pepper and sugar. Cook over medium heat for about 5 minutes. Drain potatoes, rinse and peel.
Melt the fat in a saucepan, stir in the flour and sauté until light yellow, stirring constantly. Deglaze with stock and milk while stirring, stir until smooth, bring to the boil, remove from heat and allow to swell for approx. 5 minutes in a closed pot.
Season with salt, pepper and nutmeg. Grease an ovenproof dish (1.5 litre capacity). Spread the bottom with some béchamel sauce. Mix potatoes, carrots and minced meat and put half of it into the baking dish.
Spread the rest of the béchamel sauce over it. Add the rest of the minced meat mixture. Grate the gouda finely and sprinkle over it. Bake in a preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for approx. 30 minutes.
Remove and garnish with parsley.