A cheddar, broccoli and potato soup built in the slow cooker, thickened mostly by mashing some of its own potatoes.
Twenty minutes of preparation, five to six hours of cooking, and a careful ten minutes at the end.
Why This Recipe Works
- Mashing part of the potato is the thickening. There is no flour and no roux in this recipe, which is also what keeps it naturally gluten-free if the broth is.
- Yukon Golds are waxy enough to hold their cubes but starchy enough to mash well — the one potato that does both jobs in the same pot.
- Milk and cream together rather than either alone. All milk is thin; all cream is heavy and more prone to splitting. A cup of each is the balance.
- Adding the cheese last and off the boil is what separates a smooth soup from a grainy one. Three cups is a lot of cheese and it needs the temperature respected.
Five Steps, and the Heat Only Goes Down
The temperature in this recipe steps down as it goes — Low, then High, then Low or Warm — and each drop protects something that has just been added. Reverse any of them and you can see the result in the bowl.
Steps 1 and 2
Potatoes cooked VERY tender, then some mashed
Very tender, not just tender. The mashing in step 2 is what gives this soup its body - there is no roux anywhere - and a potato that still has structure will not break down under a masher.
Step 3, on High
Broccoli for 20 to 30 minutes only
Small florets, added after the potatoes are done rather than with them. Broccoli in from the start would be olive-coloured mush after five hours; this window softens it while it still looks like broccoli.
Step 4
Milk, cream and cornstarch whisked TOGETHER first
Combining the slurry with the dairy in a bowl before it goes in means the starch is evenly dispersed. Cornstarch tipped straight into a hot pot clumps, and those lumps never come out.
Step 5
Switch to Low or Warm BEFORE the cheese
This is the rule that matters most, and it is the whole ballgame. Cheese proteins tighten and squeeze out their fat above a simmer, which is what makes a cheese soup grainy and oily. The heat has to come down first.
Step 5, still
Cheddar added GRADUALLY
Three cups dumped in at once cools the soup unevenly and clumps. Handfuls, stirred through, let each addition melt before the next arrives.
Ingredient Notes
- Yukon Gold potatoes
- Two pounds in one-inch cubes. Waxy enough to keep some shape, starchy enough to mash — both properties are used here.
- Chicken or vegetable broth
- Five cups, and the choice decides whether the recipe is vegetarian. Nothing else in it is animal-derived except the dairy.
- Freshly shredded sharp cheddar
- Three cups, and freshly shredded is a specification rather than a nicety. Pre-shredded cheese is the main cause of a grainy result.
- Cornstarch and cold water
- Two tablespoons each, whisked into the dairy rather than added to the pot alone.
How to Make It
Cook the potatoes
Cook the potatoes, onion, garlic, broth, salt, pepper and thyme on Low for 4.5 to 5 hours, until very tender.
Mash for body
Mash some of the potatoes to thicken the soup.
Broccoli
Add the broccoli florets and cook on High for 20 to 30 minutes.
Thicken
Whisk the milk, cream and the cornstarch slurry together, stir them in, and cook 10 to 15 minutes.
Cheese, off the boil
Switch to Low or Warm and stir in the cheddar gradually, without letting the soup boil.
Success Tips
- Cook the potatoes past tender so they mash properly.
- Add the broccoli late; it only needs 20 to 30 minutes.
- Never let the soup boil after the cheese goes in.
- Shred your own cheddar and add it in handfuls.
Serving Ideas
Crusty bread or a bread bowl, and more cheddar at the table. It is rich, so something sharp alongside — a salad with a vinegary dressing — earns its place.
Storage and Reheating
Refrigerate
Refrigerate up to 3 days. It thickens as it cools; loosen with a splash of broth or milk when reheating.
Freeze
Not recommended. Cheese-and-cream soups separate on thawing and cooked potato turns grainy.
Reheat
Gently, below a simmer, stirring. The same rule as the cooking applies: heat is what breaks a cheese soup, and reheated is exactly when people forget it.
Frequently Asked Questions
My soup went grainy.
Either the cheese was pre-shredded, or the soup was still boiling when it went in. Both are common and both are avoidable — shred your own, and drop the cooker to Low or Warm before a single handful of cheddar arrives.
It was thinner than I expected.
Probably not enough potato was mashed. That mashing is the main thickener here, so be more thorough with it — and make sure the potatoes were genuinely very tender first, because firm ones will not break down.
Can I make it vegetarian?
Yes, and the recipe already allows for it: use the vegetable broth option. Nothing else in the ingredient list is animal-derived apart from the milk, cream and cheese.
