Instructions: 

1. Preheat oven to 375 degrees.
2. Bring 4 quarts (3.8 liters) of lightly salted water to a boil. Add pasta to water, return water to a gentle boil and cook for 10-12 minutes or until al dente, stirring intermittently. Drain.
3. Meanwhile, place a deep-sided saucepan over medium heat, adding enough oil to cover the bottom. Season chicken breasts with salt & pepper to taste and add to pan, cooking each side for about 7 minutes. Remove from pan and set aside. When cool enough, shred into bite-sized pieces.
4. Use the same pan and bring to medium heat. Add bacon and cook until crispy. Remove bacon from pan with a slotted spoon and drain on a paper towel. Carefully tip out bacon into a cup and place pan back on medium-low heat.
5. Measure out 2-3 tablespoons of reserved bacon fat and add back into the pan. Add about 1-2 tablespoons butter. Add flour and whisk constantly until a roux forms and turns a bit toasty and golden. Pour in milk and whisk to incorporate, occasionally stirring, until thickened. Dip a spoon into the béchamel and run a finger down the back of the spoon. If the béchamel does not run together then it is ready (or known as nape).
6. Turn the heat to low and add fontina, cheddar, smoked mozzarella, and Parmesan, stirring until the cheeses are melted. Add pasta, chicken and bacon, and season with cayenne and salt & pepper.
7. Tip mixture into a greased 9" x 13" baking dish. Top with Panko, a few knobs of butter and more Parmesan, if desired. Bake the dish for 30 minutes, or until bubbly. For a crunchier topping, broil for a few minutes before removing from oven. Let rest for 5-10 minutes before serving.