Boil the pasta: Cook the pasta in well-salted water until just shy of al dente. Reserve 1 cup of pasta water, then drain.
Season the chicken: Pat the chicken dry and season with salt, pepper, and 1/2 teaspoon Italian seasoning.
Sear the chicken: Heat olive oil in a large skillet over medium-high.
Add chicken in a single layer and cook until golden and cooked through, 5–7 minutes. Transfer to a plate.
Sauté aromatics: Lower heat to medium. Add butter, then the shallot and garlic.
Cook 1–2 minutes until fragrant, not browned. Stir in remaining Italian seasoning, red pepper flakes, and sun-dried tomatoes for 30 seconds.
Build the sauce: Pour in chicken broth and simmer 2–3 minutes to reduce slightly. Lower heat to medium-low.
Stir in cream cheese until melted and smooth.
Finish creamy base: Add heavy cream and half of the Parmesan. Stir until silky. If it’s too thick, splash in pasta water to loosen.
Add veggies: Stir in cherry tomatoes and spinach.
Cook 1–2 minutes until spinach wilts and tomatoes soften slightly.
Combine: Return chicken and its juices to the skillet. Add drained pasta and toss to coat. Use pasta water as needed to create a glossy, clingy sauce.
Season and serve: Taste and adjust with salt and pepper.
Turn off heat and fold in basil and remaining Parmesan. Serve hot with extra cheese and a crack of black pepper.