Add the butter to dutch oven and heat over MED heat. Add chopped onion and saute until onions are soft and translucent, about 2-3 minutes. Add the minced garlic and saute for another 30 seconds.
Slowly pour in the bone broth. Add the broccoli, mustard, paprika, nutmeg, and pepper, stir and cover with a lid.
Reduce heat to LOW/MED LOW and simmer about 10 minutes or until broccoli is fork tender.
Add one cup of cream.
Sprinkle Xanthan gum and blend soup until desired texture is reached, using either immersion blender or by transferring soup to traditional blender.
Turn the heat off.
Add grated cheddar cheese a handful at a time, stirring to melt the cheese into the soup after each handful. Taste soup and add salt if needed.
If soup gets too thick for your liking, add a splash of chicken broth or cream to loosen it up.
Serve hot with additional black pepper and shredded cheese on top if desired.
Soup can be refrigerated for up to 3 days, Not good for freezing.