Heat oil in a Dutch oven or large saucepan over medium-high heat. Add onion, carrot and celery; cook, stirring often, until the onion and celery soften, 5 to 6 minutes. Add potato and garlic; cook, stirring, for 2 minutes. Stir in flour, dry mustard and cayenne; cook, stirring often, for 2 minutes.Advertisement
Add broth and broccoli stems; bring to a boil. Cover and reduce heat to medium. Simmer, stirring occasionally, for 10 minutes. Stir in florets; simmer, covered, until the broccoli is tender, about 10 minutes more. Transfer 2 cups of the chowder to a bowl and mash; return to the pan.
Stir in Cheddar and sour cream; cook over medium heat, stirring, until the cheese is melted and the chowder is heated through, about 2 minutes. Season with salt.
Make Ahead Tip: Prepare through Step 2. Cover and refrigerate for up to 2 days or freeze for up to 2 months.
Ingredient note: Most supermarkets sell broccoli crowns, which are the tops of the bunches, with the stalks cut off. Although crowns are more expensive than entire bunches, they are convenient and there is considerably less waste.
1 starch, 1 vegetable, 1 high-fat meat