Peel and finely dice the onion and garlic. Peel, wash and finely dice the carrot. Wash, quarter and seed 2 tomatoes. Finely dice the flesh. Wash, clean and slice 2 tomatoes.
Heat the oil in a frying pan. Fry the minced meat in portions until golden brown. Remove. Sauté onion and garlic in frying fat. Add diced carrots and tomatoes and fry briefly. Add minced meat, strained tomatoes and herbs and let it boil down for about 20 minutes.
In the meantime wash and clean the beans and cut them in half crosswise. Cook the beans in boiling salted water for about 5 minutes. Drain and let drain. Heat fat in a pot, add flour while stirring and sweat for about 1 minute.
Deglaze with milk, stirring constantly and simmering for about 5 minutes. Season with salt, pepper and nutmeg. Season the minced sauce with salt, pepper and sugar. Layer the béchamel sauce, pasta plates, minced sauce and beans alternately in an ovenproof casserole dish.
Add tomato slices and crumbled feta cheese. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 45 minutes. Remove and serve garnished with oregano.