Bring a large pot of water to a boil. Salt generously. Add the pasta and cook until al dente. Reserve a mug full (about 1 cup) of the pasta water then drain the pasta. Return the pasta to the pot.
While the pasta is cooking, cut the bacon into bite-sized pieces. Cook in a large skillet over medium-high heat until crisp. Remove the bacon with a slotted spoon to a plate lined with paper towels to drain.
Add the butter to the bacon grease in the skillet and cook until the butter is melted. Whisk in the flour and cook for a minute or two.
Slowly whisk in the chicken broth and the cream. Cook for a few minutes, until the sauce has started to thicken up. Add in the Parmesan and stir until melted.
Pour the Alfredo sauce and the reserved bacon over the pasta in the pot. Stir to coat. If needed, add some of the reserved pasta water to loosen up the sauce.
Serve topped with chopped parsley, if desired.
