There is something quietly satisfying about a pot of soup made from vegetables that have spent the morning in the ground. In Somerset, where the soil holds the damp and the frosts arrive late but sharp, root vegetables are the backbone of winter cooking. Parsnips sweeten after a cold snap, carrots grow earthy and dense, and onions keep for months in a cool shed or garage.
A roasted root vegetable soup is the sort of lunch that suits family life here: it costs very little, it stretches a bag of odds and ends into four generous bowls, and it can be made in the gap between the school run and the afternoon. Better still, it asks nothing of you but a hot oven and a bit of patience.
The beauty of this soup is that the recipe is really a method. Use whatever is rattling around the veg rack, the bottom of the fridge, or the basket by the back door.
Aim for roughly 1kg of prepared vegetables in total. Soft, bendy carrots are perfectly fine here, as are parsnips with a few brown patches, so long as you cut the blemishes away. If an onion has begun to sprout, halve it and discard the green shoot. This is a soup that rewards thrift rather than punishing it.
You could boil the vegetables and blend them, and you would end up with something perfectly edible. Roasting them first, though, is what turns the same ingredients into a soup with depth. The natural sugars caramelise, the edges catch and darken, and the finished bowl tastes far richer than the shopping list suggests.
Heat the oven to 200°C (180°C fan, gas mark 6). Cut everything into rough 3cm chunks – no need for precision, but keep them a similar size so they cook evenly. Tip them into a large roasting tin with 3 tablespoons of olive or rapeseed oil, a good pinch of flaky salt and plenty of black pepper. Add 4 unpeeled garlic cloves and a few sprigs of thyme or rosemary.
Toss everything with your hands until each piece is glossy, then spread it out in a single layer. If the tin looks crowded, use two – crowded vegetables steam instead of roasting. Give them 35 to 45 minutes, turning once or twice, until the edges are deep golden and the parsnip tips are just beginning to catch. Check at 30 minutes; parsnips can turn bitter if they blacken.
Once the vegetables are tender enough to squash against the side of the tin, tip them into a large pan and pour in about 300ml of hot stock. Add the roasted garlic cloves, squeezed from their skins, and discard the woody herb stalks.
Blend in batches until completely smooth, or leave it slightly chunky if your family prefers texture. Now loosen it gradually with more stock – somewhere between 700ml and 1 litre in total – until it pours from a spoon in a slow, velvety ribbon rather than a plop. A soup that is too thick will taste heavy; a soup that is too thin will taste watery. Add, stir, taste.
Finish with a knob of butter or a splash of cream, then taste again for salt. Root vegetables need generous seasoning, and what tasted right before blending often needs a little more afterwards. A teaspoon of cider vinegar or a squeeze of lemon will lift the whole pan if the flavour seems flat.
This is a soup that welcomes company. Set out a few bowls of toppings and let everyone build their own, which tends to head off the usual complaints from the smaller members of the household.
For a lunchbox or flask, blend it a little thinner so it stays drinkable as it cools, and pour it in piping hot. It also freezes beautifully in single portions, which makes it a reliable fallback on a grey Tuesday when the fridge looks bare.
Keep the peelings, tops and trimmings in a bag in the freezer and simmer them with an onion and a bay leaf for 40 minutes to make your own stock. Strain it, and you have the base for next week's soup at no cost at all.
Leftover roast vegetables from Sunday can go straight into the pan, too – just warm them through in stock and blend. Cooked soup keeps for four days in the fridge and three months in the freezer; label it with the date and what went in, because everything blended looks the same once it is frozen. And remember that the recipe is only a guide. Whatever your garden, veg box or greengrocer has given you this week is exactly what belongs in the pot.