Creating the French Onion Chicken Orzo Casserole is easy when you follow these clear steps:

1. Preheat Oven: Begin by preheating your oven to 375°F (190°C).
2. Cook Chicken: Season the chicken breasts with salt and pepper. In a large skillet, heat olive oil over medium heat. Cook the chicken for about 5-7 minutes per side, until golden brown. Remove from skillet and set aside to cool slightly, then slice into bite-sized pieces.
3. Caramelize Onions: In the same skillet, melt butter over medium heat. Add the sliced onions and cook for about 15 minutes, stirring frequently, until they are golden brown and soft. Add the minced garlic and thyme, cooking for an additional 2 minutes.
4. Cook Orzo: In a separate pot, bring the broth to a boil. Add the orzo and cook until al dente, about 8-10 minutes. Drain and set aside.
5. Combine Ingredients: In a large mixing bowl, combine the cooked orzo, sliced chicken, caramelized onions, and heavy cream (if using). Mix well to incorporate all the flavors.
6. Add Cheese: Fold in about 1 ½ cups of shredded cheese, reserving the remaining amount for topping.
7. Transfer to Baking Dish: Pour the mixture into a greased 9×13 inch baking dish. Spread it evenly and top with the remaining cheese.
8. Bake: Place the dish in the preheated oven and bake for 30-35 minutes, or until the cheese is bubbly and golden brown.
9. Garnish: Once baked, remove from the oven and let it sit for a few minutes before serving. Garnish with fresh parsley to add a pop of color.

Following these steps will lead you to a wonderfully aromatic and comforting casserole that is bound to impress!