If the chicken breasts are thick, slice them horizontally into cutlets or pound them to an even thickness. Pat them dry, then season with about 3/4 teaspoon kosher salt and all of the black pepper.

Heat the olive oil in a large skillet over medium-high heat. Sear the chicken for about 4 to 5 minutes per side, until golden brown and nearly cooked through, then transfer it to a plate.

Reduce the heat to medium and add the minced garlic and sliced sun-dried tomatoes. Cook for 30 to 60 seconds, just until the garlic is fragrant.

Pour in the chicken broth and scrape the browned bits from the bottom of the skillet. Simmer for 2 to 3 minutes so the broth absorbs the savory pan flavor.

Stir in the heavy cream, Parmesan, Italian seasoning, and remaining salt. Simmer gently for 2 to 4 minutes, avoiding an aggressive boil, until the sauce begins to thicken.

Add the baby spinach if using and stir until the leaves wilt. Return the chicken and any juices from the plate to the skillet.

Spoon the sauce over the chicken and simmer for 2 to 4 minutes, until the chicken reaches 165°F internally and the sauce is creamy. Garnish with chopped basil or parsley before serving.