Pound chicken breasts to even thickness (about three-quarters inch), then season generously with salt, black pepper, and Italian seasoning on both sides. Cook in olive oil over medium-high heat for 5-6 minutes per side until golden and internal temperature reaches 165°F, then set aside to rest for 3 minutes.
While chicken rests, bring salted water to a rolling boil and add pasta, cooking according to package directions until al dente (usually 9-11 minutes). Reserve one cup of pasta water before draining.
In the same pan used for chicken, melt 6 tablespoons butter over medium heat and add minced garlic, stirring constantly for 1-2 minutes until fragrant but not browned.
Pour in chicken broth and heavy cream, whisking to combine smoothly, then add grated parmesan cheese while stirring constantly for 2-3 minutes until the sauce thickens and becomes creamy. This garlicky buttery italian chicken pasta achieves its signature silky texture through the emulsification of butter, cream, and cheese working together.
Slice rested chicken into bite-sized pieces and return to the pan with cooked pasta, fresh spinach, lemon juice, and red pepper flakes. Toss everything together for 1-2 minutes until spinach wilts and pasta coats evenly, adding reserved pasta water if the sauce seems too thick.