Boil the pasta. Bring a large pot of salted water to a boil. Cook the fettuccine until just shy of al dente. Reserve about 1/2 cup of pasta water, then drain and set aside.

Crisp the bacon. In a large skillet over medium heat, cook the chopped bacon until browned and crisp. Transfer the bacon to a paper towel–lined plate. Leave about 2 tablespoons of bacon fat in the skillet; pour off the rest.

Season the chicken. Pat the chicken dry. Toss with salt, pepper, and Italian seasoning so the pieces are evenly coated.

Brown the chicken. In the same skillet with the bacon fat, add the chicken in a single layer. Cook 4–6 minutes, stirring occasionally, until golden and cooked through. Transfer to a bowl and tent loosely with foil.

Start the sauce base. Reduce the heat to medium-low. Add the butter to the skillet. When melted, stir in the garlic and cook 30–45 seconds until fragrant. Don’t brown the garlic.

Add cream and milk. Pour in the heavy cream and milk, scraping up any browned bits. Simmer gently for 2–3 minutes to warm through. Keep the heat low so the dairy doesn’t scorch.

Melt in the cheese. Sprinkle in the Parmesan gradually, whisking until smooth. If the sauce feels too thick, loosen it with a splash of reserved pasta water. You want a glossy, pourable consistency that coats a spoon.

Combine everything. Return the chicken and half the bacon to the skillet. Add the cooked pasta and toss to coat. Let it simmer on low for 1 minute so the pasta absorbs the sauce.

Finish and adjust. Taste and adjust salt and pepper. If you like a hint of heat, add a pinch of red pepper flakes. For brightness, squeeze in a little lemon.

Serve. Top with the remaining bacon, extra Parmesan, and chopped parsley. Serve hot.