Heat 2 tablespoons olive oil in a large skillet over medium heat. Season 4 boneless, skinless chicken breasts with salt and pepper on both sides, then add them to the skillet. Cook for about 5 to 7 minutes per side, until golden brown and cooked through. Remove the chicken and set it aside.
In the same skillet, melt 2 tablespoons unsalted butter. Stir in 1 cup diced Vidalia onion and cook for 3 to 4 minutes, until softened. Add 1 tablespoon minced garlic (about 3 cloves) and 1 teaspoon Italian seasoning and cook for another 30 seconds, until fragrant.
Stir in 1 cup uncooked orzo and let it toast for a minute or two, coating it in the butter and aromatics. Pour in 1/2 cup dry white wine and deglaze the pan, scraping up the browned bits. Let the wine simmer for a few minutes.
Pour in 1 1/2 cups chicken broth, the juice from one lemon, and the seeded lemon slices. Stir gently and bring to a gentle simmer. Cook for 10 to 12 minutes, until the orzo is almost tender.
Stir in 1/2 cup heavy cream and the lemon zest. Add 2 cups loosely chopped baby spinach and 3/4 cup freshly grated Parmesan cheese, and cook just until the spinach wilts and the sauce is creamy.
Remove the lemon slices. Slice the cooked chicken and place it on top of the orzo. Serve right away with extra Parmesan and a squeeze of fresh lemon if desired.