Season the chicken breasts with salt and pepper on both sides.
In a large skillet, heat the olive oil over medium-high heat. Add the chicken breasts and sear for about 6-7 minutes on each side, or until cooked through and golden brown. Remove the chicken from the skillet and set aside.
In the same skillet, add the chopped onion and minced garlic. Sauté for about 2-3 minutes, or until the onions are translucent and fragrant.
Gradually add the fresh spinach to the skillet, stirring until wilted. This should take about 2 minutes.
Lower the heat and pour in the heavy cream. Stir in the parmesan cheese and Italian herbs. Allow the mixture to simmer gently for about 3-4 minutes until slightly thickened.
Slice the cooked chicken into strips and return it to the skillet, coating it well with the creamy spinach sauce.
Add a squeeze of fresh lemon juice for brightness and season with additional salt, pepper, and red pepper flakes if desired. Serve warm.
Notes
Serve directly from the skillet for a rustic look, garnished with extra parmesan cheese and a sprinkle of fresh herbs.