Heat the olive oil in a large frying pan, add the finely chopped onion and grated garlic, fry over low heat until soft and translucent. Increase the heat and add the minced meat. When the meat is almost fried, add the broth, passata, tomato puree, basil, oregano, salt and pepper. Simmer for 12-15 minutes. Set aside to cool down.
Cook the pasta (al dente) according to the instructions on the package. Make sure you don’t overcook it. Rinse with cold water and set aside.
Tomato sauce: cook all the tomato sauce ingredients in a small frying pan for about 10 minutes until slightly reduced.
Béchamel sauce: melt the butter in a saucepan, whisk in the flour until smooth (without lumps). Constantly stirring, add the milk, cook for a while until a thick, creamy sauce is obtained. Season with salt and nutmeg and mix well.
Preheat the oven to 180°C.
Spread the reduced tomato sauce on the bottom of a large ovenproof dish. Stuff the shells with meat sauce one by one and place them in the prepared dish. Add béchamel sauce on top and sprinkle with a grated Parmesan. Put the prepared meal in the oven and bake for about 20 minutes. Enjoy your meal!