Creamy Cheesy Carrot Casserole

2 pounds carrots, peeled, sliced diagonal 3/4 inch pieces

2 tablespoons butter

1 large onion, finely chopped

2 tablespoons all-purpose flour

1 1/2 teaspoons salt

1/2 teaspoon ground black pepper

1 teaspoon dry mustard

1/2 teaspoon dried thyme

1/4 teaspoon dried sage

1/4 teaspoon ground nutmeg

1 1/2 cups milk

1 cup cheddar cheese, shredded

1 cup panko crumbs

Preheat oven to 350 degrees. Prepare a casserole dish by greasing with non-stick cooking spray. Set aside. Place the chopped carrots into a sauce pan and add water until the carrots are covered by about 1/2 inch. Add 1 teaspoon of salt. Over medium-high heat, bring carrots to a boil. Once water has come to a full boil, cook the carrots for 10-12 minutes. Remove from heat and drain. Set aside. While the carrots are cooking, add the butter and onions to a large skillet. Sauté the onions over medium heat until cooked through – about 4-5 minutes. Don't brown the onions, but they should be soft and translucent. Sprinkle the flour into the onion and butter mixture. Use a whisk to combine and to continuously move the flour around the pan. The flour will be absorbed by the onions and the butter. Once you see no more white flour, continue to cook for 2-3 minutes, while continuing to whisk. Next, add the salt, ground black pepper, dry mustard, thyme, sage, and nutmeg. Whisk into the onion mixture. Add 1/2 cup of milk and whisk into the onion mixture. Once the flour and onion mixture has been fully whisked into the milk and the mixture begins to thicken, add another1/2 cup milk and repeat until once again the mixture has thickened. Repeat this action with the last 1/2 cup milk. Once all the milk has been added and the sauce is thick, turn off the heat and add the cheese. Stir the cheese into the sauce until melted. Arrange the carrots into an even layer in the casserole dish. Ladle the cheese sauce evenly over the carrots. Sprinkle over the panko crumbs. Bake for 25 minutes. Remove from oven; garnish and serve immediately.