Serves 4 50g butter 1.4 litres water 1 large white onion, peeled and finely chopped, or 2 bunches of spring onions, trimmed and finely chopped 1 bay leaf 5 thyme sprigs 700g new Juliette potatoes, washed and coarsely chopped 1 tsp salt 450g ripe tomatoes, skinned, deseeded and finely chopped 4 tbsp olive oil Small bunch of basil, leaves only red wine vinegar, to taste salt and pepper
Melt the butter in a large pan with a little of the water, and add the onion, bay leaf and thyme. Stew over a low heat for a few minutes, then add the potatoes and salt. Cover and simmer for 5 minutes. Pour in the rest of the water and bring to the boil. Cook until the potatoes are falling apart. Blitz the soup in a liquidiser and pass through a sieve into a clean saucepan. In another saucepan, fry the tomatoes with a little seasoning in 1 tbsp of the olive oil, and cook until their juices have evaporated and the tomatoes have thickened slightly. Blitz the tomatoes in a liquidizer and pass through a sieve into the potato soup and mix well. Place the basil into the bowl of the liquidizer, add a splash of red wine vinegar, a little salt and the remaining olive oil. Leave the liquidizer running for some time to make the basil dressing. Serve the soup warm in individual bowls with a spoonful of the basil puree floating on top and a generous grinding of pepper. If the soup thickens between the time it is made and served, thin it with additional water or, if you prefer, a little cream.