Chilled radish, watercress and tahini yogurt soup

Method

1. Melt the butter in a medium saucepan with a lid over a low-medium heat. Add the leek and garlic, cover, then cook for about 5 minutes, stirring often. Add the radishes and cook for 1-2 minutes, then add the watercress and cook for 1-2 minutes more.
2. Pour in the vegetable stock, season with salt and pepper, then simmer for 5 minutes, no longer.
3. Meanwhile, whisk the tahini with the yogurt in a bowl. Once the soup has finished simmering, purée the mixture in the pan with a stick blender, then add the tahini and yogurt mixture. Blend again until well incorporated and frothy. Pour into a bowl, cool, then chill. Stir in a squeeze of lemon juice and drizzle over some olive oil. Serve with thinly sliced radishes and bread.