In a generous pot of boiling salted water, cook the orecchiette al dente, according to package directions.
In a large saucepan or pot, heat the butter and briefly sauté the bacon. Add the onion and leek and continue to sauté until translucent.
Add the flour to the pan and whisk to combine. Add the white wine and whisk for 30 seconds, then add the milk and cream. Bring to a boil and simmer for 8 to 10 minutes, scraping the bottom of the pan occasionally to make sure the sauce doesn’t stick.
Add the Cheddar and 90 g (3 oz) of the grated Parmesan. Stir to combine, taste the sauce and adjust the seasonings as necessary, then add the truffle oil.
Toss the cooked pasta with the cheese sauce and spoon into a large ovenproof serving dish or several individual dishes.
In a small bowl combine the remaining Parmesan, chopped Italian parsley, chopped basil and / or thyme, and fresh bread crumbs.
Top the pasta with this mixture and place under the broiler for 1-2 minutes until nicely browned.
Serve with an arugula salad and a fresh tomato ragout.