Pat chicken breasts dry and season generously with salt and pepper.

Heat olive oil and one tablespoon of butter in a large skillet over medium-high heat. Place chicken in pan, not overcrowding, and sear for 4-6 minutes per side until golden brown and cooked through (internal temp 165°F). Transfer to a plate and set aside.

Reduce heat to medium, add remaining butter, minced garlic and red pepper flakes if using. Sauté for 30 seconds until fragrant.

Pour in chicken broth and scrape up any browned bits from the bottom of the pan. Let simmer for a minute.

Stir in heavy cream, Parmesan cheese, sundried tomatoes and Italian seasoning. Simmer for 3-5 minutes until sauce thickens slightly. Adjust seasoning with salt and pepper.

If using spinach, stir it into the sauce and let wilt for a minute or two.

Return chicken to the skillet, nestling it into the sauce. Spoon sauce over chicken and warm through for about a minute.

Garnish with fresh basil or parsley and serve immediately.