Masterclass

Roast the pumpkin

If there’s one thing that you can do to improve your pumpkin soup, it’s roasting. There are three main reasons why this is the game-changer.

Firstly, roasting significantly intensifies the flavour of the pumpkin by reducing the amount of water it contains. One kilogram of raw pumpkin will yield about 500 grams of roasted pumpkin flesh after cooking. Aside from leaving behind the seeds and skin, a lot of water is removed in the cooking. This is also why I don’t oil the pumpkin before roasting – you want to dry it out a bit.

Secondly, roasting rather than boiling develops more complex flavours. Higher temperatures break down longer-chain starches in the pumpkin to produce sweeter compounds over time. Maillard reactions (sugar-protein reactions) and caramelisation (sugar oxidisation reactions) occur more quickly at higher temperatures.

Boiling simply can’t achieve this. Water boils at around 100C, which is too low for significant caramelisation to occur. Caramelisation starts to kick in around 105C for fructose and up to 170C for sucrose.

By baking at 160C fan-forced, you hit that sweet spot. It’s hot enough to encourage those complex Maillard reactions and some caramelisation without burning or blackening the pumpkin, giving you a far more flavourful result.

In all, this means your long-roasted pumpkin will taste more intense, complex and sweeter than pumpkin that is boiled for 20 minutes. And when the key ingredient in your soup is pumpkin, the better you make it taste, the better your soup will be.

The final benefit of roasting pumpkin has nothing to do with taste. It’s just easier. Pumpkin can be difficult to cut if your knife isn’t sharp or heavy enough, so roasting half a pumpkin as it is makes easy work of it. Once cooked, you can scoop out the parts you want with a spoon.

Sweetness v umami

The balance of sweetness and umami is a powerful one in food. It’s what makes oyster sauce a perfect stir-fry seasoning, or Worcestershire sauce a great addition to stews, and it’s why the great Tetsuya Wakuda once told me that when you add soy sauce to a dish (umami), its taste should be balanced with a pinch of sugar (sweetness).

In pumpkin soup, the sweetness comes naturally from the roasted pumpkin, and we balance that with umami-tasting stock. All stocks are umami-tasting liquids, which is why they make great ingredients in savoury cooking.

Cook a pumpkin in water and you can turn it into desserts such as pumpkin pie or pudding, but if you dial up the umami, that’s what makes a great pumpkin soup.

Some people like to add umami ingredients such as miso or soy sauce, but I prefer to keep it simple by using a good stock, then fortifying it with a spoonful of stock powder.

Blending hot liquids

Perhaps it’s controversial, but for me, pumpkin soup has to be velvety smooth.

Blending hot liquids can be tricky. When you blend hot liquids, you’re essentially creating a lot more surface area, which leads to rapid steam release. In a sealed blender, this steam builds up pressure, and that’s when things can get a bit dicey.

The good news is, there’s a simple fix. Remove the stopper from the lid of your blender and cover the opening with a tea towel. This allows the steam to escape safely. Make sure you start blending on a low speed and gradually increase it. This prevents a sudden surge of steam and manages the pressure.

Alternatively, you can use a stick blender, but it can be difficult to get a silky consistency.

Importantly, blending will change the taste profile of the soup. The process releases additional sweetness from the chunks of pumpkin into the soup, so make sure you taste and season the soup again after blending.

Variations

I have kept this pumpkin soup recipe very classic, but there are endless opportunities to put your own spin on it.

• Spice the soup with 2 teaspoons of your favourite curry powder added when frying the onion, carrot and celery.
• Add ginger along with this mirepoix.
• Add red curry paste or miso.
• Replace the cream with coconut cream.
• Roast the pumpkin with rosemary.
• Crumble blue cheese over the top.
• Spread your grilled bread with pesto or soft goat’s curd.
• Serve it with croutons mixed with roasted almonds, or with mushrooms on toast.

All of these are excellent variations that will ensure that your classic pumpkin soup never gets boring.