A bowl that earns its place on a grey afternoon

There is a particular kind of British afternoon in late autumn and winter where the light never quite arrives and the rain settles in sideways against the window. These are the days when a salad feels like an insult and a heavy pie leaves you wanting a nap. Lentil soup sits neatly in the middle: substantial enough to feel like a proper meal, light enough that you can go back to work, and cheap enough that a pot costs less than a couple of coffees.

It also happens to be one of the most forgiving things you can cook. If you can chop a few vegetables and stir a pot, you can make this, and the results improve rather than suffer when you make it in a big batch on a Sunday.

Why lentils are kind to a sensitive gut

Lentils are pulses, and pulses have a reputation for causing wind. That reputation is not entirely unfair, but it is not the whole story either. Lentils provide soluble fibre, which feeds the beneficial bacteria in your large intestine and helps keep things moving without the harshness of a bran-heavy breakfast. They also contain resistant starch, particularly in the firmer varieties, which ferments slowly and steadily rather than all at once.

The trick is how you treat them. A few practical points make a real difference if your digestion is easily unsettled:

• Rinse them well. Red lentils from the shop carry dust and surface starch. Two or three changes of cold water until it runs clear makes for a cleaner-tasting soup.
• Cook them until they collapse. Underdone lentils are harder work for a sensitive gut than soft, well-cooked ones.
• Start with a small bowl. If pulses are new to you, half a portion for the first few times lets your gut bacteria adapt. They usually do, given a fortnight or so.
• Go easy on the onion and garlic if you know these trigger you. More on that below, because there are simple swaps.

Lentils are naturally gluten-free, which makes this soup a reliable option for anyone avoiding wheat, provided you check your stock.

What goes in the pot

This makes four generous bowls, or six smaller ones. The quantities are loose on purpose — root vegetables are forgiving, and using up what is in the drawer is rather the point.

• 250g red lentils, rinsed
• 1 tbsp olive oil or rapeseed oil
• 2 carrots, 1 parsnip and a quarter of a swede, all diced small
• 2 celery sticks, sliced
• 1 leek, sliced, or the green tops only if onion bothers you
• 2 cloves garlic, crushed (or 1 tbsp garlic-infused oil)
• 1 tsp ground cumin, 1 tsp smoked paprika, ½ tsp dried thyme
• 2 bay leaves
• 1.2 litres vegetable or chicken stock
• Juice of half a lemon, a handful of spinach or shredded kale, salt and black pepper

Do check your stock cubes and powders if you are avoiding gluten or dairy — some contain wheat-derived ingredients and milk powder, and they are easy to overlook.

Method: half an hour, mostly hands off

Warm the oil in a large pan over a medium heat. Add the carrot, parsnip, swede, celery and leek with a good pinch of salt. Cook gently for eight to ten minutes until the vegetables soften and smell sweet rather than raw. This step is worth the patience; it builds the flavour that makes the soup taste homemade rather than merely healthy.

Stir in the garlic, cumin, paprika and thyme and cook for another minute until fragrant. Add the lentils, bay leaves and stock, bring to a gentle simmer, then cover and cook for 20 to 25 minutes, stirring now and then, until the lentils have broken down and the roots are tender.

Fish out the bay leaves. If you like a smoother soup, blitz half of it with a stick blender and leave the rest chunky. Stir through the lemon juice and the greens, let them wilt for a minute, then season to taste. The lemon is not optional — it lifts the whole pot and stops it tasting flat.

Serve with a spoonful of natural yoghurt or a drizzle of good olive oil, and bread if you are hungry.

Freezing, reheating and busy weeks

This soup freezes beautifully, which is half its appeal. Cool it quickly, portion into containers and freeze for up to three months. It thickens as it sits, so loosen with a splash of water or stock when reheating on the hob or in the microwave. Reheat until piping hot throughout and only once — do not refreeze a portion you have already warmed up.

A note on keeping it interesting across a week: freeze in smaller portions and add something fresh each time you reheat. A handful of spinach, a spoon of yoghurt, a scatter of toasted seeds or a little chopped parsley makes Tuesday's bowl feel different from Sunday's.

Tweaks for different guts and different evenings

If onion and garlic reliably cause bloating, use the green tops of leeks or spring onions instead, and swap the garlic for garlic-infused oil, which carries the flavour without the fructans. A pinch of asafoetida does something similar. If you are following a low-FODMAP approach, keep portions modest and build up gradually.

For a smokier version, add a chopped roasted red pepper with the stock. For something more substantial, stir in a drained tin of chickpeas in the last five minutes. And if you want it creamier without dairy, a spoonful of coconut milk works surprisingly well with the cumin and paprika.

Made once, eaten three times, and better on the second day — that is a fair return on half an hour at the hob.