Lasagna

Preheat the oven at 180° C.

For the ragu, heat a large skillet and add the oil. Add the minced meat to the pan and fry it until it gets a golden brown crust all around. Remove the pan from the heat and spoon the meat onto a plate. Add the onion, celery (if using) and garlic to the pan and fry until everything is soft. Return the meat to the pan and stir in the flour. Add the broth and bring to a boil. Add the sugar, tomato paste and thyme and stir well.

Stir in the Passata. Bring to a boil again, cover and simmer in the oven for 1 to 1 1⁄2 hours or until the minced meat is tender.

Melt the butter in a sauce pan for the white sauce. Add the flour and stir well so you don't get any lumps. Let it simmer for a while so that the flour taste disappears completely. Gradually whisk in the warm milk and keep whisking until the sauce thickens. Add the Dijon mustard and parmesan and season well with salt and pepper.

For the lasagna, spread a third of the meat sauce over the bottom of a deep 2.3-liter ovenproof dish. Spoon a third of the white sauce on top. Arrange a layer of lasagna sheets on top. Season with salt and pepper. Spoon half of the remaining meat sauce on top, followed by half of the white sauce. Top this with another layer of lasagna sheets. Finish with the remaining meat sauce and the remaining white sauce. Sprinkle with the cheddar.

Slide the dish into the center of the oven for about 45 minutes or until the lasagna turns golden brown, bubbles at the corners and the pasta is soft.