Warm leek soup with a cool spoonful

Method

1. Wash the leeks properly

   Trim the roots and dark green tops, then split the leeks lengthways and wash between every layer. Slice them thinly. Grit hides in the folds, and it is much easier to remove now than from a finished bowl.

   Warm the olive oil in a wide saucepan over medium heat. Add the onion and leeks with a pinch of salt and cook for ten minutes, stirring often, until soft but not browned. Slow cooking gives the soup its sweetness.

2. Build the soup

   Add the garlic and thyme for one minute, then stir in the potato, beans and hot stock. Bring to a gentle simmer and cook uncovered for 20 minutes, or until the potato is tender. Keep the bubbles quiet so the beans do not break apart before you decide how smooth the soup should be.

   Taste the stock halfway through. If it is already salty, wait before adding more. Beans and stock vary, and the final finish may bring more seasoning.

   

3. Blend to the texture you want

   Blend two ladlefuls of soup until smooth and stir it back into the pan. This thickens the stock while leaving some beans and leek visible. For a completely smooth soup, blend the whole batch in stages and return it to the saucepan over low heat.

   A stick blender makes a rougher, more homestyle texture. A jug blender makes it silkier, but never fill it more than halfway with hot liquid and vent the lid so pressure can escape.

4. Add the ${v.finish}

   Stir the yogurt with lemon zest, lemon juice, garlic, olive oil and a pinch of salt. Let the soup stand for two minutes, then spoon yogurt over each bowl.

   If the soup has tightened while standing, add a splash of hot stock. It should coat a spoon lightly and still pour easily into a bowl.

5. Rest and serve

   Leave the soup off the heat for five minutes, then taste once more for salt, pepper and lemon. Serve in warmed bowls with the finish visible on the surface.

   The leeks should taste sweet, the beans should make the stock feel rounded, and the potato should have disappeared into the body rather than sitting as hard cubes. That is the check that the timing has worked.