Fresh Spring Asparagus Soup

1. In a large sauté pan, heat oil or butter. Add leek, onion and potato and sauté on medium heat until softened.
2. Add asparagus and herbs and sauté another 1-2 minutes.
3. Add stock, bring to boil, reduce to simmer and simmer for about 10-15 minutes or until everything is tender enough to be put through a blender.
4. Blend in small batches (or use an immersion blender), adding yogurt and salt and pepper to each batch.
5. Serve garnished with additional yogurt if desired, but serve immediately. This soup is best consumed within a few hours of making it, but it will keep for a couple of days in the fridge (just with a stronger flavour).