Sweet potato soup is the one soup where we can skip the cream and still lose nothing in terms of creaminess. The reason lies in the vegetable itself.
Sweet potatoes contain more soluble starch and considerably more natural sweetness than ordinary potatoes. Once cooked and blended, they thicken the broth on their own and give it a velvety texture. In our standard version we add 150 g of double cream because it rounds off the heat from the chilli, but if you leave it out you will not end up with a watery soup. The consistency stands or falls with the sweet potato.
Sweet Potato Soup with the Thermomix®
Ingredients 0 / 10 ✓
- 1 onion
- 2 garlic cloves
- 1/2 chilli
- 30 g sunflower oil
- 600 g sweet potato
- 200 g carrot
- 1200 g vegetable stock
- 1/2 tsp salt
- 2 tbsp soy sauce
- 150 g double cream
Instructions 0 / 6
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1
Chop the vegetables.
Peel the onion and garlic, halve the onion, place in the mixing bowl together with the chilli, chop for 5 seconds / speed 6 and scrape down with the spatula.
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2
Sweat.
Add the oil and cook for 3 minutes / Varoma / speed 1.
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3
Prepare the sweet potatoes and carrots.
Meanwhile, peel the sweet potatoes and carrots and cut into pieces.
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4
Steam the vegetables.
Add the vegetables and cook for a further 3 minutes / Varoma / speed 1.
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5
Cook the soup.
Add the vegetable stock and salt and cook for 20 minutes / 100°C / speed 1.
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6
Blend and serve.
Blend the soup by gradually increasing to speed 8, add the soy sauce and double cream and cook for a further 3 minutes / 100°C / speed 1.
Tip: If you are cooking for children, leave out the chilli and season the soup to taste at the end.
Video
Nutrition per serving
Why sweet potato cooks differently to ordinary potato
The vegetable we use here is botanically not a potato. Sweet potatoes belong to the morning glory family and have a higher sugar content within their starch structure. Two things happen at the same time during cooking: the starch gelatinises from around 70 °C and binds liquid, while enzymes convert part of the complex starch into maltose. That is exactly why the soup tastes sweeter cooked than raw, and becomes thicker at the same time.
We make the most of this by simmering the 600 g of sweet potatoes and 200 g of carrots for 20 minutes at 100°C on speed 1. Speed 1 is perfectly sufficient because we are going to blend everything up to speed 8 at the end anyway. If you impatiently stir on speed 3 beforehand, you break up the pieces too early and release starch into the water. That makes the soup cloudy instead of creamy. Better to let it cook quietly for 20 minutes and then blend it smooth in one go.
Why soy sauce belongs in this recipe
The 2 tbsp of soy sauce added at the end are not an Asian gimmick. They provide glutamates and salt in a form that gives the sweetness of the vegetable a savoury foundation. Without this step the soup tastes too much like a dessert. We add it after blending and let it cook for 3 minutes at 100°C on speed 1. That way the flavour is absorbed rather than sitting raw in the finished dish.
The half chilli goes in right at the beginning with the onion and garlic, 5 seconds at speed 6. This distributes the heat evenly throughout the soup. If you want to play it safe, deseed the chilli first. The heat sits in the white membranes around the seeds; the flesh itself is considerably milder.
When the soup turns out too sweet
We have had this happen more than once: depending on the variety, sweet potatoes can be significantly higher in sugar, especially if they have been stored for a few weeks. Storage converts more starch into sugar. If the finished soup tastes too sweet, three things help:
- stir in a generous squeeze of lime juice at the end, the acidity pulls the sweetness back
- add another half tsp of salt or 1 tbsp of soy sauce to shift the flavour towards savoury
- add a generous amount of freshly ground black pepper, which noticeably dampens the perception of sweetness
The carrots are not just padding here. 200 g of carrots balance out the sweetness of the sweet potato because, while they bring their own sweetness, they also add earthiness and more fibre structure. If you remove them and top up with extra sweet potato, the balance tips. The soup becomes mushy and too sweet at the same time.
Asian twist with ginger, coconut milk and lime
If you want to push the soup in a Thai-style direction, it is easy to do. Instead of the 150 g of double cream, we use 200 g of coconut milk and add it after blending. In addition, a roughly 2 cm piece of fresh ginger goes into the mixing bowl together with the onion and garlic, also for 5 seconds at speed 6. We stir in the juice of half a lime only just before serving, as the acidity evaporates during cooking.
The combination of 600 g sweet potato, ginger, coconut milk and lime works so well because each ingredient covers a different flavour dimension: sweetness from the vegetable, spice and warmth from the ginger, fat and softness from the coconut milk, acidity from the lime. Salt and glutamate come from the soy sauce. That is a complete flavour framework without any further seasoning. Fresh coriander leaves or toasted peanuts as a topping are optional but not needed for the flavour.
Further variations that work well for us
With apple and curry: We replace 100 g of the carrots with a peeled apple cut into pieces and add 1 tsp of mild curry powder with the oil to the mixing bowl. The apple intensifies the sweetness while the curry provides the necessary seasoning. Great for the colder months.
With toasted pumpkin seeds: Toast 30 g of pumpkin seeds in a dry pan for 5 minutes, chop roughly and scatter over the soup before serving. The crunch makes the difference between an everyday recipe and a dish fit for guests.
Vegan without cream: Leave out the cream entirely and add a dollop of natural soya yoghurt to each bowl just before serving. The soup itself is stable thanks to the sweet potato starch; the yoghurt provides the visual creaminess.
With lentils for extra substance: Add 80 g of red lentils along with the vegetable stock, then cook for 25 minutes instead of 20 minutes at 100°C on speed 1. The lentils break down completely and make the soup more filling without affecting the texture.
Storing and reheating
The soup keeps for 3 days in the fridge in a sealed jar or airtight container. We prefer to reheat it in the mixing bowl: 8 minutes at 90°C on speed 1 is enough for the remaining quantity from 4 servings. When reheating, the starch thickens further, so the soup is often even thicker on the second day than when freshly made. If it becomes too thick, simply stir in 50 to 100 g of hot water or stock.
Freezing works well in single-portion containers for up to 3 months. The only thing we recommend leaving out before freezing is the cream, as it can separate slightly on thawing. Cook the soup all the way through to the blending stage, pour into containers to cool, and add fresh cream only when reheating. That way it tastes just as good after thawing as when freshly made.
What we like to serve alongside
Sweet potato soup is filling on its own, but on cold evenings we love to have a freshly baked spelt bread alongside it, dipped in olive oil. For something heartier, fry 100 g of streaky bacon or chorizo cubes in a pan and scatter the crispy pieces over the soup. That gives the sweet vegetable a salty, smoky counterpoint.
As a homemade stock base, we most often use our vegetable paste made in the Thermomix® or a seasoning paste for meat stock. Both are free from flavour enhancers and provide the clean, rounded stock foundation that the sweet potato needs. If you do not have freshly made stock to hand, at least use a good-quality organic stock without yeast extract.
Looking for more cream soups made with the Thermomix®? Here are our most-cooked:
- Beetroot Soup
- Creamy Mushroom Soup
- Cheese and Leek Soup
- Pizza Soup
- Pumpkin Soup
- Courgette Soup
- Cauliflower Soup
- Tomato Soup
- Peking Soup
Orange or white sweet potato: which one goes in the mixing bowl
Goes well with: Ciabatta.
The supermarket usually stocks two varieties: the orange Beauregard and the pale yellow to white Japanese sweet potato. For our soup we always use the orange variety. It has more beta-carotene, a more intense colour and a moister starch content that delivers the silky consistency in the Thermomix®. The white variety is drier and more floury, which makes it better suited to chips or fritters. Most Cookidoo recipes work with 500 g sweet potato and 400 g coconut milk. We deliberately go for 600 g sweet potato and 200 g double cream or coconut milk, because that ratio gives a creamier result and carries the natural sweetness without the soup tipping into excess fat.
