Preheat your oven to 350°F (175°C). Cook dry spaghetti according to package instructions until just shy of al dente, about 6-7 minutes. Drain and mix in melted butter, Romano cheese, and beaten eggs until well combined. Press the mixture into the bottom and up the sides of a greased pie plate, then refrigerate to firm, around 15 minutes.

While the crust sets, heat a large skillet over medium heat. Cook bacon until crispy, about 5-7 minutes, then reserve the fat. In the same pan, sauté chopped onion, red bell pepper, and minced garlic in the bacon fat until softened, around 3-4 minutes. Add diced chicken and cook until it’s no longer pink, about 5 minutes, then remove from heat.

In a separate saucepan, melt 2 tablespoons of butter over medium heat. Whisk in all-purpose flour and cook for 1 minute. Gradually add whole milk and heavy cream, stirring constantly, until the sauce thickens, about 3-5 minutes. Season with salt, black pepper, dry mustard, and nutmeg. Stir in the chicken mixture and the cooked bacon, followed by cubed Fontina cheese until melted and creamy.

Spread ricotta cheese evenly over the chilled spaghetti crust, creating a smooth layer. Pour the creamy chicken carbonara filling on top, spreading it out evenly, and top with shredded mozzarella. Bake in the preheated oven for about 40 minutes or until the cheese is bubbly and golden brown.

Once out of the oven, let the Chicken Carbonara Spaghetti Pie sit for 20 minutes, covering it with foil to keep warm. This resting period helps the pie set for easier slicing. Serve with a light green salad or garlic bread to complement the rich, cheesy flavors.