Preheat oven to 350 degrees F.
In large pot of boiling salted water, cook the macaroni to al dente (approximately 7 minutes). Strain and place on a lightly oiled sheet pan.
While the macaroni is cooking, in a separate pot, melt 3 tablespoons of butter and whisk in the flour.
Continue to cook over low heat for 4 minutes stirring constantly. Add the milk, chopped truffles, onion and bay leaf. Simmer for 10 minutes. Remove onion and bay leaf.
Turn off the heat and add 3/4 of the aged cheddar and all of the other cheeses. Season with salt and black pepper and fold in macaroni. Pour into a 2-quart casserole dish. Top with remaining cheddar.
Melt the remaining butter in a sauté pan and toss bread crumbs and parsley to coat. Top the macaroni with bread crumb mixture. Bake for 30 minutes. Remove from the oven let stand for about 5 minutes. Serve with fresh shaved black truffles.