Preheat oven to 350°. Lightly spray a 2-qt or larger baking dish with nonstick cooking spray.
Place carrot slices in a large pot and just cover with salted water. Bring to a boil and cook carrots until tender; about 10 minutes.
Drain carrots and place them in a large bowl. Add butter and milk and mash with a potato masher. Add onion, cheese, salt, pepper, garlic powder, thyme and parsley and mash together to desired smoothness.
Place into prepared baking dish.
In a small bowl, combine 1 tbsp melted butter with the breadcrumbs; sprinkle over mashed carrot mixture.
Bake, uncovered, at 350° for 30 - 40 minutes or until bubbly.