Preheat the oven to 375°F (190°C). In a large oven-safe skillet, heat a drizzle of olive oil over medium heat. Add chopped onion, eggplant, and shallot. Cook for about 5 minutes, until softened. Stir in cherry tomatoes and cook a few more minutes until vegetables are coated and tender.
In a bowl, whisk together chicken broth, garlic powder, Italian seasoning, and salt.
To the skillet, add uncooked orzo, rotisserie chicken, sun-dried tomatoes, spinach, and chopped basil. Pour the broth mixture over and stir well to combine.
Cover and bake for 20 minutes. Remove from oven, uncover, and stir in Greek yogurt until creamy and evenly mixed. Smooth the top.
Sprinkle with remaining feta. Return to oven uncovered and bake for 10 more minutes. For a golden top, broil for 1–2 minutes at the end if desired. Let rest for 5 minutes before serving. Garnish with fresh basil or extra feta, and enjoy.