Preheat your oven to 375°F (190°C).

Heat olive oil in a large skillet over medium heat. Sear the chicken breasts for about 5 minutes on each side until browned. Remove from skillet and set aside.

In the same skillet, add the chopped onion and minced garlic. Sauté until the onion is translucent.

Toss in the broccoli, sliced carrots, and frozen peas. Cook for about 5 minutes until the vegetables are slightly tender.

In a bowl, combine the cream of mushroom soup, sour cream, milk, thyme, rosemary, salt, and pepper. Mix until smooth.

Stir in the sautéed vegetables to coat them in the creamy sauce.

Spread half of this vegetable mixture on the bottom of a greased 9×13 inch baking dish. Place the seared chicken breasts on top.

Pour the remaining vegetable mixture over the chicken, ensuring it’s well-covered.

Sprinkle shredded cheddar cheese evenly over the casserole.

In a separate bowl, mix the breadcrumbs with melted butter, then sprinkle this over the top for crunch.

Cover with aluminum foil and bake in the preheated oven for 25 minutes.

Remove foil and bake for an additional 10-15 minutes until the top is golden brown and bubbly.

Let sit for 5 minutes before serving to allow it to set.