Prepare the asparagus by breaking off and discarding the woody ends, cutting off and reserving the tips and slicing the stalks into 1cm chunks. Add the asparagus tips to a small saucepan of boiling salted water and blanch for 3 minutes. Drain and set aside.
Bring a second saucepan of salted water to a boil, lower to a gentle simmer and keep to one side. Heat the olive oil in a non-stick frying pan, add the leek and cook, stirring, for 5 minutes until browned.
Add the asparagus stalks, season with salt and cook for 20 minutes, stirring occasionally and adding a ladleful of hot water every 5 minutes to prevent everything sticking to the bottom of the pan, until the asparagus stalks are soft and cooked through.
Tip the asparagus and leek mixture into a food processor and blend together well. Set aside. Preheat the oven to 180C/gas mark 4. Grease a 35cm x 20cm oven dish with a little butter.
Gently heat the milk in a small saucepan, ensuring it doesn’t boil. In a separate saucepan, melt the butter, add the nutmeg and flour and stir together to make a smooth paste (roux).
Season with salt and slowly add the warm milk, stirring constantly, to form a smooth, creamy sauce. Bring to a gentle boil, then remove from the heat and set aside.
Bring a large saucepan of salted water to a boil, add the pasta and cook for half of the cooking time indicated on the packet, or about 3-7 minutes.
Drain and place in a bowl along with the sauce, two-thirds of the provola and half of the blended asparagus. Mix everything together well and pour into the prepared oven dish.
Scatter over the asparagus tips and pancetta cubes, pour over the remaining asparagus mixture and sprinkle with the remaining provola. Transfer to the oven and bake for 20-25 minutes, or until the surface has formed a nice golden crust.
Sprinkle over the breadcrumbs and cut into rectangles. Serve hot or cold.