Preheat oven to 375°F (190°C). Toss chicken with olive oil, salt and pepper.
1.5 lbs boneless, skinless chicken breasts, 1 tablespoon olive oil, 1/2 teaspoon salt, 1/4 teaspoon black pepper
Melt butter in a large skillet over medium heat. Add onions, sugar, salt, and pepper. Cook, stirring occasionally, until onions are deeply caramelized (about 30-40 minutes).
3 large yellow onions, 2 tablespoons butter, 1 teaspoon sugar, 1/4 teaspoon salt, 1/4 teaspoon black pepper
While the onions are cooking, place the cut chicken in a 9x13 inch baking dish. Add uncooked orzo and 5 cups of chicken broth. Stir to combine.
1.5 lbs boneless, skinless chicken breasts, 1 cup orzo pasta, 6 cups chicken broth
Sprinkle flour over caramelized onions and stir constantly and add them to the baking dish with the chicken and orzo.
3 large yellow onions, 2 tablespoons all-purpose flour
Add white wine and Worcestershire sauce to the baking dish. Stir to combine. Top with thyme and the remaining chicken broth.
1/2 cup dry white wine, 1 teaspoon Worcestershire sauce, 1/2 teaspoon dried thyme, 6 cups chicken broth
Cover the dish with foil and bake for 45 minutes. Remove the foil and bake for another 15 minutes, or until the orzo is tender and the chicken is cooked through.
Sprinkle Gruyere and Parmesan cheese evenly over the casserole.
1 cup shredded Gruyere cheese, 1/2 cup shredded Parmesan cheese
Broil for 2-3 minutes, or until the cheese is melted and bubbly, watching carefully to prevent burning.
Let stand for 5-10 minutes before serving. Garnish with fresh parsley, if desired.
1/4 cup chopped fresh parsley
