anne burrell's killer mac & cheese with bacon

from anne burrell's "cook like a rock star"

ingredients:

• extra virgin olive oil
• 6 slices bacon, cut crosswise into 1/2-inch strips
• 3 tablespoons unsalted butter
• 1 onion, cut into 1/4-inch dice
• kosher salt
• 1/2 cup all-purpose flour
• 1 quart whole milk, plus more as needed
• 1 pound shells or other short pasta
• 2 cups freshly grated cheddar cheese
• 2 cups freshly grated fontina cheese
• 1 cup freshly grated parmigiano
• 1/4 dijon mustard
• tabasco or other hot sauce, to taste

directions:

• drizzle a bit of olive oil in a large saucepan, add the bacon, and bring the pan to medium heat; stir the bacon ocassionally. when it's brown and crispy, 6 to 8 minutes, remove it from the pan, drain on paper towels, and reserve. DO NOT DISCARD the bacon fat!
• add the butter and onion to the pan with the fat, season with salt, and cook until the onion is soft and aromatic, 8 to 10 minutes. add the flour and cook, stirring frequently, for 4 to 5 minutes or until the mixture looks like wet sand. slowly whisk in the milk, season with salt, bring to a boil and reduce to a simmer; cook over low heat for 8 to 10 minutes more or until the mixture is slightly thicker than heavy cream.
• in the meanwhile, bring a large pot of well-salted water to a boil. add the pasta to the boiling water and cook for one minute less than the instruction on the package suggest. taste it. it should be toothsome with just a little nugget of hard pasta still in the center- this is al dente. drain the pasta and reserve.
• add the cheddar, fontina, and parmigiano to the milk mixture and whisk to combine. add the mustard and a few shakes of the tabasco; taste and adjust the seasoning if needed, adding a little more milk if the mixture seems too thick. stir in the bacon and pasta. the mixture should be very creamy and flavorful. 
• serve immediately or transfer to a baking dish and reheat in a  375 degree oven.