In a large soup pot, melt butter. Add onion and cook until soft, 5 minutes. Whisk in flour and let cook 2 minutes. Add chicken broth and season generously with salt and pepper.
Stir in broccoli, carrots, and celery and simmer until vegetables are tender, 20 minutes.
Reduce heat to low and add milk. Bring to a simmer and stir in cheddar.
Season with salt and pepper and top with more cheddar.
Serve with baguette.
Recipe by Cooking TV Recipes at https://cookingtv-channel.com/broccoli-cheddar-soup/