Put the milk, onion, bay leaves and cloves into a large saucepan and bring very gently lasagna puttanesca up to the boil. Turn off the heat and set aside for 1 hr to infuse. For the meat sauce, put the oil, celery, onion, carrot, garlic and pancetta in another large saucepan. Gently cook together until the veg is soft but not coloured.
Tip in the beef and pork mince, the milk and chopped tomatoes. Using a wooden spoon, stir together and break up and mash the lumps of mince against the sides of the pan. When the mince is mostly broken down, stir in all the herbs, the stock cubes and the red wine, and bring to a simmer. Cover and cook for 1 hr, stirring occasionally to stop the bottom catching.
Uncover and gently simmer for another 30 mins-1 hr until the meat is tender and saucy. To finish the béchamel sauce, strain the milk through a fine sieve into one or two jugs. Melt the butter in the same pan then, using a wooden spoon, mix in the flour and cook for 2 mins. Gently bubble for a few minutes until thickened. Season with salt, pepper and a good grating of nutmeg. Spread a spoonful of the meat sauce over the base of a roughly 3.