Step 1

Flavor Base: Set a large pot over medium heat. Add butter, onion, carrots, celery, and garlic. Stir and cook until onion is soft and translucent, about 5 minutes.

Step 2

Soupify: Stir in flour to evenly coat the veggies. Stir in broth, broccoli, and cauliflower. Bring to a gentle simmer, then cover and let cook until broccoli is fork-tender.

Step 3

Blend: Scoop about half of the fillings from the pot. Blend the half that remains until smooth (using either a handheld immersion blender, or by carefully transferring to a countertop blender*). Stir reserved solids back into soup.

Step 4

Finish: Stir in cheese and mustard. Taste and add salt as needed. Serve hot, topped with shredded cheese, crusty bread, and/or a dollop of sour cream.