Preheat your oven to 375°F (190°C).

In a large skillet, heat 2 tablespoons of olive oil over medium heat. Add the chopped onion and minced garlic, sautéing for 2-3 minutes until translucent.

Add the diced chicken breast to the skillet and sear for 5-7 minutes, stirring occasionally until browned on all sides.

Pour in 2 cups of chicken broth and bring to a gentle simmer. Add 1 cup of heavy cream, 1 tablespoon of Dijon mustard, and the dried thyme and rosemary. Season with salt and pepper, and let simmer for about 5 minutes.

Stir in 1 cup of shredded cheddar cheese until melted and creamy.

In a large bowl, combine the chicken mixture with 2 cups of cooked rice and stir gently.

Pour the mixture into a greased 9x13 inch casserole dish and smooth the top.

In a separate bowl, mix 1 cup of breadcrumbs with ½ cup of grated Parmesan cheese and 2 tablespoons of melted butter.

Sprinkle the breadcrumb topping evenly over the casserole. Bake for 25-30 minutes until golden brown.

Let the casserole cool for a few minutes and garnish with freshly chopped parsley before serving.