1. Cook the carrots by steaming or boiling gently in water. Drain, season with salt and pepper to taste, and place in a greased baking dish.
2. Melt the butter in a saute pan. Add the onion and cook until tender and translucent. Add the flour and stir until smooth. Gradually add the milk, stirring constantly to keep lumps from forming until the milk is all combined. Cook and stir until thickened and bubbly. Add the cheese and stir until melted. Add additional salt and pepper to taste.
3. Pour the sauce over the carrots and stir gently to combine. Bake at 350ºF for 30-35 minutes.
Makes 8 servings.