In a large pot over medium heat, 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. Bring to a boil and reduce heat to low. Let simmer until vegetables are tender, 20 minutes.
Add milk and bring to a simmer, then stir in cheddar.
Season with salt and pepper and top with more cheddar. Serve with baguette.
Recipe by 5* trending recipes with videos at https://food.theffeed.com/2020/03/02/broccoli-cheddar-soup/