Preheat the oven to 350°F. Set out an 8x8-inch baking dish.
Place sliced carrots in a steamer basket over a pot with 1-inch of boiling water. Cook for about 10 minutes, or until carrots are fork tender. Alternatively, place carrots in a glass bowl and use the steam setting on your microwave for about 4 minutes, or until carrots are done. Set aside.
In a medium saucepan over medium-high heat, melt 1 tablespoon of butter. Add the onion and cook for 2 minutes, stirring frequently until softened. Stir in flour, garlic powder, salt, and pepper.
Gradually whisk in the milk. Continue cooking for 1 minute to thicken. Turn the heat down to low.
Add the cheese, stirring until completely melted. Fold in the carrots. Pour the mixture into the baking dish, spreading carrots so they are in an even layer.
In a small bowl, stir together the crushed cracker crumbs and remaining 1 tablespoon butter. Sprinkle over the top of the casserole.
Bake 15 minutes, or until topping is lightly golden. Garnish with a sprinkling of parsley and serve hot.