Cook the macaroni following pack instructions until al dente. Drain, rinse with cold water and set aside to cool.
Tip the milk and bay leaves into a pan and bring to a simmer. Remove from the heat. Melt the butter in a large non-stick saucepan, then stir in the flour to make a thick paste, continuing to stir for 3-4 mins. Remove and discard the bay leaves from the milk, then gradually pour it into the flour and butter mix, continuously stirring to keep the sauce smooth. Add the mustard, thyme, truffle paste and porcini powder, then stir in the taleggio cheese and mozzarella until melted slightly. Remove from the heat, tip in the macaroni and stir to coat. Scrape into an ovenproof dish. Will keep chilled for up to 24 hrs.
Heat the oven to 200C/180C fan/gas 6. Sprinkle over the cheddar, breadcrumbs and parmesan, and bake for 20 mins until golden. For a crispy top, grill for 5 mins or until just golden. Serve straightaway.
