Prep the chicken: Pat the chicken dry and season generously with salt and pepper. Cutting the chicken into similar-size pieces helps it cook evenly and quickly.

Heat the skillet: Place a large skillet over medium-high heat and add olive oil. When it shimmers, add the chicken in a single layer. Don’t crowd the pan—work in batches if needed.

Get a good sear: Let the chicken cook without moving it for 2 to 3 minutes, then flip and cook another 2 to 3 minutes until golden and mostly cooked through. Transfer to a plate and cover loosely.

Build the flavor base: Lower the heat to medium. Add the butter to the skillet. Once melted, stir in the garlic and cook 30 to 60 seconds until fragrant. Avoid browning the garlic—it should smell sweet, not bitter.

Deglaze the pan: Pour in the chicken broth and scrape up any browned bits with a wooden spoon. Let it simmer for 2 to 3 minutes to reduce slightly.

Make it creamy: Stir in the cream (if using), Italian seasoning, and a small pinch of red pepper flakes. Simmer 1 to 2 minutes until it starts to thicken.

Add the parmesan: Reduce heat to low. Sprinkle in the parmesan gradually, stirring constantly until smooth. Keep the sauce just below a simmer so the cheese melts gently and doesn’t turn grainy.

Bring back the chicken: Return the chicken and any juices to the skillet. Toss to coat and cook 2 to 3 minutes until the chicken is cooked through and the sauce clings nicely.

Brighten it up: Stir in the lemon juice and taste. Adjust salt, pepper, and lemon as needed. If the sauce is too thick, splash in a bit more broth.

Finish and serve: Fold in spinach or tomatoes now if using, just until wilted or warmed. Sprinkle with parsley and extra parmesan. Serve hot over pasta, rice, mashed potatoes, or with grilled bread.