Start by bringing a pot of salted water to a boil and cook the spaghetti according to package instructions until it reaches al dente. Drain it but don’t rinse—keeping the starch helps the sauce cling to the noodles.
In your large skillet over medium heat, cook the bacon until it’s nice and crisp. Drain the bacon pieces and set aside, but leave about 2-3 tablespoons of bacon fat in the pan. Then season the chicken cubes with salt and pepper and sear them in the bacon fat until golden brown, working in batches if needed so you don’t crowd the pan.
Turn the heat down to low and add the garlic into the bacon fat; cook until fragrant (about 1 minute). Then pour in the chicken broth and milk. Add the cubed cream cheese, cover the pan, and cook until the cream cheese has nearly melted. Whisk in the Parmesan and let the sauce simmer uncovered on low until it thickens.
Add the cooked pasta back into the skillet along with the seared chicken and crumbled bacon. Toss everything together until the pasta is well-coated in the sauce and everything is evenly mixed. Serve immediately for the best texture.