Begin by bringing a large pot of salted water to a boil over high heat. Add the spaghetti and cook according to the package instructions, typically about 8-10 minutes, until al dente. Once cooked, reserve a cup of pasta water, drain the noodles, and set aside.

In a large skillet, heat the reserved bacon drippings over medium heat. Add the thick-cut bacon, cooking for about 5-7 minutes until crispy and golden, turning occasionally for even cooking. Once done, remove the bacon from the skillet and drain it on paper towels. Leave about 2 tablespoons of drippings in the pan.

Season the boneless skinless chicken breasts with salt and black pepper to taste. In the same skillet with the remaining bacon drippings, increase the heat to medium-high. Sear the chicken for about 4 minutes on each side until golden and cooked through, reaching an internal temperature of 165°F (75°C). Remove from the skillet and let it rest.

Reduce the heat to low, and add minced garlic to the skillet. Sauté for about 1 minute, stirring frequently until the garlic is fragrant and slightly softened but not browned.

Pour in the chicken broth and milk, then add the cream cheese to the skillet. Stir to combine, covering the pan to help the cream cheese melt, which should take about 3-5 minutes. Whisk everything together until smooth and creamy.

Add grated Parmesan cheese to the sauce, stirring to incorporate. Allow the sauce to simmer for an additional 3-5 minutes until it thickens slightly. Taste and adjust seasoning with salt and black pepper as needed.

Return the seared chicken, crumbled bacon, and cooked spaghetti to the skillet. Toss everything together over low heat for a minute, ensuring the pasta is well-coated with the creamy sauce. Serve immediately.