Season the chicken breasts generously on both sides with salt and pepper. Pat them dry with paper towels for better browning.

Heat olive oil in a large skillet over medium-high heat until it shimmers. The pan should be hot enough that chicken sizzles when added.

Add chicken breasts to the hot skillet without crowding. Cook for 5-6 minutes without moving them to develop a golden crust. When edges turn opaque, flip and cook another 5-6 minutes until internal temperature reaches 165°F.

Remove cooked chicken from the skillet and set aside on a plate. The chicken will continue cooking slightly from residual heat.

Lower heat to medium. Add minced garlic to the same skillet and sauté for 30 seconds, stirring constantly, until fragrant but not browned.

Pour in the cream and add Italian seasoning and Parmesan cheese. Stir until cheese melts completely and sauce becomes smooth. The sauce will thicken slightly as the cheese incorporates.

If using spinach, add it now and stir into the sauce. Let simmer for 2-3 minutes until spinach wilts and becomes tender.

Return chicken breasts to the skillet, nestling them into the sauce. Spoon the creamy sauce over each piece of chicken to coat well.

Let everything simmer together for 1 minute to meld flavors. The sauce should bubble gently around the chicken. Taste and adjust seasoning if needed, then serve immediately.