Why roots deserve a place in the winter kitchen

There is a stretch of the year — from the first hard frost to the first genuinely warm afternoon — when the garden gives up and the hedgerows give up with it. What the kitchen still has, and has in abundance, is roots. Carrots lifted in October and stored in a box of damp sand in the shed. Parsnips left in the ground until the frost sweetens them. A swede the size of a football that has been sitting on the cool shelf since bonfire night, refusing to go off.

Roots are cheap, they keep for months without refrigeration, and they roast into something far more interesting than they ever taste raw. A soup built on roasted roots is the most useful thing you can make with them: it uses up a glut, it reheats, it freezes, and it fills a flask for a walk better than almost anything else. This is a plain, dependable method rather than a recipe you need to follow to the gram.

Choosing and preparing the roots

Firm, heavy for their size, no soft patches and no black marks at the crown. That is the whole test. Beyond that, the mix is up to what you have.

• Carrots — about 400g. Maincrop types are starchier and roast better than the sweet, thin ones. Scrub rather than peel if the skins are clean; a bit of skin means a bit more flavour.
• Parsnips — about 400g. Small and medium ones are sweeter. Large ones often have a woody core; quarter them lengthways and cut it out with a knife.
• Swede — about 500g. Dense stuff, so cut it smaller than everything else, roughly 2cm dice, or it will still be hard when the carrots are done.
• Onion and garlic — one large onion, roughly chopped, and three or four cloves of garlic left whole and unpeeled.

If you have a celeriac going spare, or a couple of potatoes, they can go in too. A potato adds body and means you need less cream later.

Roasting is the step that does the work

You could boil these vegetables and blend them, and you would get soup. You would not get the deep, slightly sweet, faintly caramelised flavour that makes people ask what is in it.

Heat the oven to 200°C, or 180°C with a fan, or gas mark 6. Cut everything into roughly even 2–3cm chunks. Tip into a large bowl with three generous tablespoons of rapeseed or olive oil, a good pinch of salt and plenty of black pepper, four or five sprigs of thyme or rosemary, and a couple of bay leaves. Toss until every piece is glossy.

Spread it all out in a single layer on a large baking tray. If it looks crowded, use two trays. Crowding steams the vegetables and they never brown properly — this is the one thing worth being strict about. Roast for 35–45 minutes, turning everything once at the halfway point, until the edges are dark gold and a knife slides through a piece of swede without resistance.

If you are using one tray, give the swede a ten-minute head start before adding the rest.

Stock, simmer and season

Tip the roasted vegetables into a large pan, herbs and all, but fish out the bay leaves. Now deglaze the tray: splash in a little of your stock while it is still hot and scrape up the sticky brown bits with a wooden spoon. That residue is the best part of the whole operation, and it costs nothing to rescue.

Add 1 to 1.2 litres of stock — homemade chicken stock is ideal, a decent vegetable stock works perfectly well. Bring to a gentle simmer, not a rolling boil, and cook for 15–20 minutes. The vegetables are already cooked through, so this stage is about bringing everything together rather than softening anything.

Taste before you blend, and again afterwards. Roasted roots vary enormously in sweetness, and seasoning after blending always seems to need more salt than you expect.

Blending and finishing

A stick blender is the least fussy option. Take the pan off the heat first, and keep the blade fully submerged to avoid spattering. If you are using a jug blender, work in batches and never fill it more than half full — hot liquid expands, and the lid needs holding down with a folded tea towel.

For a velvety soup, blend it thoroughly and then loosen with a little more stock or milk. For something more substantial, pulse it and leave some texture in there.

To finish, stir through any of the following:

• Two tablespoons of crème fraîche or double cream, or a knob of butter.
• A grating of nutmeg and a lot of black pepper.
• A squeeze of orange juice or a teaspoon of honey if the swede tastes at all bitter.
• A pinch of curry powder or ground cumin, added to the oil before roasting, if you are working mostly with parsnip.

Freezing, flasking and eating it outdoors

Cool the soup quickly, then freeze in portions. Flat freezer bags stacked like paper save far more space than tubs, and a portion thaws in a pan in ten minutes. It keeps well for three months. Reheat gently and loosen with a splash of water or milk, as it thickens on standing.

For a winter walk, a wide-mouthed flask is the right tool. Fill it with boiling water first, leave it five minutes, then empty it and fill with hot soup. Leave an inch of headroom, screw the lid down firmly, and wrap the flask in a tea towel inside your pack. Take an enamel mug and a spoon.

At home, serve it with soda bread, a cheese scone, or toast with melted cheddar on top. Eaten at a kitchen table after a wet walk, or out of a mug on a gate at the top of a hill, it does the same job either way: it makes a cold evening feel considerably shorter.