Heat oil in a large pot or Dutch oven over medium-high; season chicken with salt and pepper and cook 5-6 minutes until golden brown and cooked through. Set aside.
Cook garlic in same pot 30 seconds until fragrant; add tomatoes, Italian seasoning, and optional pepper flakes and stir another minute.
Stir in dry pasta and broth, scraping up browned bits.
Boil; reduce heat to medium and simmer uncovered 10-12 minutes, stirring frequently, until pasta is almost al dente.
Reduce heat to low; stir in cream and simmer 2-3 minutes until slightly thickened.
Add spinach and return chicken; stir 1-2 minutes until spinach wilts.
Off heat, stir in Parmesan; adjust salt and pepper, garnish with fresh basil, and serve immediately.