Using asparagus for soup is a sin at the start of its season, but makes sense when the spears turn thick and woody. Samphire, or poor man's asparagus, works very well with the real thing, adding texture as well as saltiness.
1 medium potato, peeled and diced
600ml vegetable stock
1 tsp sugar
Salt and pepper
100ml Greek yoghurt
Grated zest of ½ lemon
- Chop off and discard the green of the leeks, cut them in half lengthways, wash and slice. Cut off and discard the woody base of the asparagus, then cut into 2cm-long pieces; keep the tips separate. In a big pan, sauté all the vegetables, other than the asparagus tips and samphire, in butter for four minutes, taking care they don't colour. Add stock, sugar and a little seasoning - go easy on the salt, because the samphire will add plenty - bring to a boil and simmer, lid on, for 40 minutes. Add the asparagus tips and cook for 10 minutes. Liquidise until smooth, fold in the cream and half the yoghurt, leave to cool to room temperature, then chill. While it's cooling, bring a pot of water to the boil, blanch the samphire for 30 seconds, drain and refresh.
- To serve, pour the chilled soup into bowls, add a dollop of yoghurt and swirl with the tip of a skewer. Place some samphire in the centre of the soup and garnish with lemon zest.