For vinegret, the beetroot gets its oil first

Vinegret is the salad that sits next to the Olivier on a winter festive table and somehow always runs out first. Beetroot, carrots, potatoes, sauerkraut, pickled cucumbers, a little onion and sunflower oil: earthy, sour, sweet and salty all at once. But for years my vinegret came out uniformly reddish-purple. Potatoes, carrots, cabbage, everything the same colour, as if someone had dyed it.

The trick is a small one. The beetroot gets its oil first, on its own, before it meets anything else. I dice it into a separate bowl, pour a spoonful of oil over it straight away and stir, so every cube gets a thin glossy coat. The oil slows the beetroot juice down from bleeding into everything around it. Only then do I add the other vegetables, diced to the same size, the sauerkraut and the pickled cucumbers, and fold it all together gently, without mashing. The colours stay separate: deep pink beetroot, orange carrot, golden potato, green cucumber.

Before any of that comes the boiling, and I split it over two days. The day before, I scrub the vegetables well under running water, because soil clings to beetroot and potatoes, and boil them whole in their skins. The skins keep the colour in the beetroot and stop the potatoes going watery. The beetroot goes in its own pan, since it takes longest: whole medium ones need about an hour of gentle simmering, until a knife slides in easily. The potatoes and carrots take twenty to thirty minutes.

Then the cooling. I don't leave them in the warm pan overnight. I lift them out onto a tray, let the steam escape, and once they've cooled, within two hours at most, they go into the fridge in a covered tub. My fridge runs at 5°C or below. Cold vegetables are easier to dice neatly, too: warm potato crumbles under the knife, cold potato cuts into clean cubes.

On the day itself the salad comes together in twenty minutes. I peel the beetroot over the sink, because beetroot juice gets everywhere, dice it and give it its oil. Then the potatoes, the carrots, a finely chopped small onion or a few spring onions, the pickled cucumbers in small cubes, and the sauerkraut. If the sauerkraut is very wet I squeeze it a little in a sieve, so the salad doesn't swim. Salt only at the end, and carefully, because the sauerkraut and cucumbers are already salty. A last spoonful of oil, a gentle stir, and that's it. Sometimes I add a handful of cooked beans, for a more filling bowl on a cold evening.

The finished vinegret lives in the fridge too. On the table it doesn't sit out all evening; after a couple of hours I put the bowl back in the fridge and bring it out again when someone wants more. We finish it within two days of making it. It doesn't freeze well, so I don't make more than we'll eat.

It is a very forgiving salad otherwise, and in autumn and winter, when beetroot, carrots and cabbage are at their best and cheapest, it is one of my favourite things to have in the fridge. A bowl of vinegret next to a piece of rye bread is a supper in itself.

And on the table it looks the way it should: bright and mixed, every vegetable its own colour. Somehow that makes it taste brighter too.

Vinegret. Serves 6. About 1 hour 15 minutes cooking the day before, plus cooling; 20 minutes to assemble. You need 3 medium beetroot, 3 medium potatoes, 2 carrots, 200 g sauerkraut, 3 pickled cucumbers, 1 small onion, 3–4 tbsp sunflower oil, salt. Scrub the vegetables and boil whole in their skins: beetroot about 1 hour, potatoes and carrots 20–30 minutes, until tender. Cool on a tray and refrigerate within 2 hours. Next day, peel and dice the beetroot, toss it with 1 tbsp oil. Dice the potatoes, carrots, cucumbers and onion; squeeze the sauerkraut if wet. Fold everything together with the rest of the oil and salt to taste. Keep in the fridge and eat within 2 days.