Preheat your oven to 375°F (190°C).

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

Add diced chicken breasts to the skillet and brown for 5-7 minutes.

Pour in chicken broth, and stir in heavy cream, Dijon mustard, dried thyme, and rosemary. Season with salt and pepper, then simmer for 5 minutes.

Incorporate shredded cheddar cheese into the sauce until melted.

In a large mixing bowl, combine chicken mixture with cooked rice.

Transfer mixture into a greased 9x13 inch casserole dish.

In a separate bowl, mix breadcrumbs, grated Parmesan cheese, and melted butter until well-coated.

Sprinkle breadcrumb mixture evenly over the casserole layer.

Bake for 25-30 minutes until bubbly and golden brown.

Let cool for a few minutes, then garnish with fresh parsley before serving.

Serve and enjoy with a green salad or steamed vegetables.