Prep the chicken. Place the chicken in a ziplock bag and pound the chicken flat to even out the pieces. If the chicken breasts are large, slice them in half and skip the pounding. Season both sides of each chicken breast with Italian seasoning, salt, and pepper.
Sear the chicken: Heat the two tablespoons of olive oil in a large skillet over medium-high heat. Sear the chicken until golden brown, about 5 to 6 minutes on each side, then transfer to a plate. *Please note the chicken may not be fully cooked at this point, but will continue to cook in the sauce. Using a meat thermometer is recommended*
Sauté the vegetables. Over medium heat, use the remaining tablespoon of olive oil in the same skillet. Add the onion and sauté for 2 minutes, until softened. Stir in the garlic and sun-dried tomatoes and cook until fragrant, about 1 more minute.
Add the spinach and fresh basil: Toss the spinach and fresh basil into the pan and sauté until it just starts to soften and wilt down.
Pour in the cream and cheese: Finish the sauce by adding in the heavy cream and parmesan. On medium-low heat, bring the sauce to a simmer for 1 minute, while scraping up any browned bits that may have stuck to the bottom of the pan.
Return the chicken to the pan. Nestle the chicken breasts into the sauce. Cook for about 5-6 minutes, or until the sauce is thickened and the chicken is cooked through. Remove from heat, top with a little more cheese, if desired, and serve immediately.