Spinach Yogurt Soup

This pureed spinach soup gets its creamy body from yogurt instead of heavy cream, which keeps it light while adding a pleasant tang that plays well against the earthy spinach and warm spices. Tarragon, nutmeg, and a pinch of cayenne give the soup a layered warmth that goes beyond basic spinach flavor.

The technique is a classic roux-based soup. Butter and flour cook together until bubbly, the spinach and broth go in, and then everything simmers and gets pureed. The yogurt is whisked in at the very end, off the boil. This is important because boiling yogurt causes it to curdle and separate into a grainy mess.

Puree the soup in batches, filling the blender only one-third full each time. Hot liquid expands and can blow the lid off a full blender, which is a scalding mess you want to avoid.

Kitchen Tips

• Use frozen chopped spinach with its liquid. The extra moisture adds body, and you skip the tedious work of washing and wilting fresh spinach.
• Whisk the yogurt in gradually once the soup is off the heat. Adding it all at once to a hot pot increases the risk of curdling.
• Heat the finished soup just until steaming, never simmering. Low and gentle is the rule once yogurt is in the pot.
• A lemon slice floated on each bowl adds brightness and a pretty presentation.

Variations

• Serve it chilled for a refreshing summer starter. The tangy yogurt base works beautifully cold.
• Swap tarragon for dill for a different herbal direction.
• Stir in a handful of fresh watercress before pureeing for a peppery, more complex green soup.