Place 2 chicken breasts on a cutting board and slice in half horizontally into 4 cutlets. Pat the chicken dry and sprinkle both sides with 1½ teaspoons Italian seasoning and ¼ teaspoon salt.

Heat 1 tablespoon oil in a large cast-iron skillet over medium heat. Arrange the chicken in the pan in a single layer; cook, undisturbed, until browned on the underside and an instant-read thermometer inserted into the thickest part registers 160°F, 4 to 5 minutes per side. Transfer to a clean cutting board; do not wipe the pan clean.

Reduce heat to medium-low and add the remaining 2 tablespoons oil. Add chopped shallot, minced garlic, 2 teaspoons rosemary and ¼ teaspoon crushed red pepper; cook, stirring constantly, until the shallot is softened, 1 to 2 minutes. Add 1½ cups orzo; cook, stirring often, until lightly toasted, about 1 minute.

Add 3 cups broth, ½ cup cream and the remaining ¼ teaspoon salt, stirring and scraping up any browned bits; bring to a simmer over medium-high heat. Reduce heat to maintain a gentle simmer, stirring occasionally, until the orzo is tender, about 10 minutes. Remove from heat and gradually stir in spinach until just wilted, about 2 minutes. Stir in ½ cup Parmesan, 2 teaspoons lemon zest and 2 tablespoons lemon juice. Spread into an even layer.

Slice the chicken cutlets. Arrange the sliced chicken on top of the orzo mixture in a single layer. Cover the skillet and let stand until the chicken is warmed through, about 3 minutes. Garnish with lemon zest and/or basil, if desired.