Classic lasagne

Method

1. Heat the oil in a large deep frying pan over a medium-high heat, then fry the prosciutto until crisp. Transfer to a plate using a slotted spoon.
2. For the meat sauce, add the celery and onion to the pan with a pinch of salt and pepper; cook until soft (about 10 minutes). Add the garlic and cook for another minute. Add the mince and fry for 4-5 minutes, breaking up with a wooden spoon, until browned. Stir in the tomato purée and chopped tomatoes; cook for another minute. Add the stock and simmer for 30 minutes over a low-medium heat until the sauce has thickened. Remove from the heat, season with salt and pepper, then stir in the fried prosciutto, chopped oregano and most of the basil leaves.
3. For the béchamel sauce, heat the butter in a medium heavy-based saucepan over a medium-high heat. Add the flour and stir constantly for 3-4 minutes until the mixture starts to smell biscuity. Slowly pour in 
the milk, whisking all the time, for 6-8 minutes until the sauce has thickened. Remove from the heat, stir in 20g of the parmesan and all the nutmeg, then season well with salt and pepper. Heat the oven to 200°C/180°C fan/gas 6.
4. To assemble, spread a little of the béchamel sauce over the base of the baking dish, then cover with slightly overlapping lasagne sheets. Pour over a third of the remaining white sauce, sprinkle over a little of the grated cheese and top with half the meat sauce. Cover with another layer of lasagne sheets, top with half the remaining white sauce, then all the remaining red sauce. Add the final layer of lasagne sheets, then spread with the rest of the white sauce. Scatter with the remaining grated cheese.
5. Bake the lasagne for 35-40 minutes until golden and bubbling. Serve garnished with the remaining basil.