Season chicken with salt and Italian seasoning. Melt butter in a large Dutch oven or pot over medium-high; sear chicken about 3-4 minutes per side until golden. Remove; set aside.
Cook garlic in same pot 1 minute until fragrant; add tomatoes and cook 2 minutes.
Add broth; simmer, scraping browned bits from bottom.
Return chicken; reduce heat to medium-low, cover, and simmer 15-20 minutes until cooked through and tender.
Remove chicken to cutting board; shred or dice bite-size.
Stir cream and Parmesan into broth until cheese melts and soup turns creamy; add optional pepper flakes.
Return chicken; stir in basil. Serve over rice or mashed potatoes in bowls.