Preheat the oven to 375 degrees F. Butter the bottom and sides of a 10-by-10-by-2-inch baking dish and set it aside.
Heat the oil in a large saute pan over medium heat. Add the pancetta and cook until golden brown on all sides, about 8 minutes. Remove with a slotted spoon to a plate lined with paper towels.
Add the garlic to the fat in the pan and cook until lightly golden brown, 1 minute. Whisk in the flour and cook for 1 to 2 minutes. Whisk in the hot milk, raise the heat to high and cook, whisking constantly, until thickened, 3 to about 5 minutes. Whisk in the eggs until incorporated and let cook for 1 to 2 minutes. Remove from the heat and whisk in the thyme, cayenne and all the different cheeses until completely melted. Season with salt and pepper. If the mixture appears too thick, add additional warm milk, 1/4 cup at a time.
Put the cooked macaroni in a large bowl, add the cheese sauce, reserved pancetta, and the parsley, and stir until combined. Transfer to the prepared baking dish.
Combine an additional 1/4 cup each asiago, cheddars, fontina and parmesan in a bowl and sprinkle evenly over the top. Bake until the dish is heated through and the top is a light golden brown, 12 to 15 minutes. Remove from the oven and let rest for 10 minutes before serving.
Photographs by Yunhee Kim
Recipe courtesy Bobby Flay for Food Network Magazine