A slow-cooker broccoli cheese soup: six cups of florets with shredded carrot and thyme, thickened with a cornstarch slurry and finished with three cups of sharp cheddar.
Fifteen minutes of prep, four or five hours on Low, and about half an hour of finishing at the end. Eight servings.
Why This Recipe Works
- The thickening comes from a cornstarch slurry rather than from potato or a flour roux. That keeps the soup tasting of broccoli and cheese rather than of starch, and it is why this recipe contains no potato at all.
- Broccoli chopped small rather than left as large florets. Small pieces soften evenly in four to five hours and distribute through the bowl, and they are also what makes the optional blending step easy to control.
- Two shredded carrots are doing more than colour. Shredded rather than sliced, they melt into the soup over the cook and bring a background sweetness that balances three cups of sharp cheddar.
- The cheese goes in after the heat comes down, in handfuls. Dumping three cups in at once drops the temperature unevenly and leaves clumps that never quite integrate.
- Equal parts whole milk and heavy cream. The cream carries the fat that keeps the cheese in suspension; the milk keeps it from being so rich that a bowl is too much.
Four Points Where A Cheese Soup Turns
A slow-cooker vegetable soup is hard to ruin right up until the cheese goes in. These are the four moments that decide whether it comes out velvety or grainy.
The cheese, before you start
Shredded from a block, not out of a bag.
Pre-shredded cheese carries an anti-caking coating of starch or cellulose. It does not melt cleanly and it is one of the two usual causes of a gritty texture.
Step 3, the blend
Optional — decide how smooth you want it before you reach for a blender.
The recipe offers two to three cups blended and returned, or a light pass with an immersion blender leaving texture. Neither is wrong; blending the whole pot loses the visible florets that make it look like broccoli soup.
Step 5, the slurry
Cornstarch into COLD water first, then into the pot, then High.
Dry cornstarch hits hot liquid and seizes into lumps that never disperse. And it needs the ten to fifteen minutes on High to actually thicken — a slurry stirred in on Low simply sits there.
Steps 6 and 7, the cheese
Heat down to Low or Warm, cheese in a handful at a time, and no boiling afterwards.
Above a simmer the proteins in cheddar tighten and squeeze out their fat, which is what separates a smooth soup into grains and grease. This is stated twice in the recipe because it is the failure that matters.
Ingredient Notes
- Broccoli florets, chopped small
- Six cups, and the defining ingredient of the recipe. Chopped small so they cook evenly and so the optional blend can be partial rather than total.
- Freshly shredded sharp cheddar
- Three cups, shredded from a block. Sharp rather than mild — at this volume of liquid a mild cheddar reads as little more than salt.
- Carrots, shredded
- Two, shredded rather than sliced. They dissolve into the soup and sweeten it; sliced rounds would sit in the bowl as separate pieces.
- Cornstarch and cold water
- Three tablespoons of each, whisked in a separate bowl. This is the only thickener in the recipe, which is why the ten to fifteen minutes on High is not skippable.
- Broth, chicken or vegetable
- Four cups, either one — the recipe offers both, and vegetable broth makes the whole soup meat-free without any other change.
How to Make It
Load the cooker
Add the broccoli, onion, carrots, garlic, broth, salt, pepper and thyme to the slow cooker.
Cook on Low
Cover and cook on LOW 4 to 5 hours, until the broccoli and carrots are tender.
Blend as much as you want to
For a smoother soup, blend 2 to 3 cups of the soup and return it to the cooker, or lightly use an immersion blender while leaving texture.
Stir in the dairy
Stir in the milk and cream.
Thicken on High
Whisk the cornstarch with the cold water and stir it in. Cook on HIGH 10 to 15 minutes, until slightly thickened.
Add the cheddar off the boil
Turn to LOW or WARM. Add the cheddar a handful at a time, stirring until melted.
Serve without boiling
Do not boil after adding the cheese; serve hot.
Success Tips
- Grate the cheddar from a block; bagged shreds are coated to resist melting.
- Chop the florets small so they soften evenly over four to five hours.
- Decide how smooth you want it before blending — you cannot un-blend a pot.
- Give the slurry its full time on High or the soup will stay thin.
- Drop the heat before the cheese and add it a handful at a time.
Serving Ideas
In deep bowls, or in a hollowed round loaf if you want the version in the photograph. Crusty bread on the side does the same job with less ceremony.
Storage and Reheating
Refrigerate
Refrigerate up to 3 days. It thickens in the fridge and loosens again with gentle heat and a splash of milk.
Freeze
Not recommended. Cheese and cream soups separate on thawing and broccoli goes drab and soft.
Reheat
Low and slow on the hob, stirring, and never to a boil — the same rule that applied when the cheese first went in.
Frequently Asked Questions
Should there be potato in this?
No. This recipe contains no potato — broccoli is the defining ingredient and the thickening comes from a cornstarch slurry.
Why did my soup turn grainy?
Almost always one of two things: bagged pre-shredded cheese, which is coated with anti-caking starch, or letting the soup get too hot after the cheese went in. Shred from a block and keep it on Low or Warm.
How much should I blend?
Entirely up to you — the step is optional. Two to three cups blended and stirred back gives a creamy base with visible florets; a light pass with an immersion blender does something similar. Blending everything gives a smooth purée and loses the texture.
Can I make it vegetarian?
Yes, without changing anything else — the recipe already offers vegetable broth as an equal alternative to chicken broth.
