Heat olive oil in a large soup pot or Dutch oven over medium heat. When hot, add leeks and cook for 5-6 minutes or until soft.
2 tablespoons olive oil, 1 large leek
Add potatoes and vegetable stock. Cook for 15-20 minutes or until potato is almost fork tender.
1 medium potato, 4 cups vegetable stock or chicken stock
While cooking, blanch reserved asparagus tips in boiling water for 1-2 minutes and then plunge them into ice water. Drain and set aside.
1 ½ pounds fresh asparagus
Add remaining asparagus pieces to soup pot and cook for another 3-5 minutes, or until asparagus is tender.
1 ½ pounds fresh asparagus
Transfer to blender in batches or use an immersion blender to blend soup. Return soup to pot and add 1 tablespoon freshly squeezed lemon juice, salt, pepper, and tarragon. Stir well, taste, and adjust seasoning to taste.
1 tablespoon lemon or lime juice, 1 teaspoon salt, ¼ teaspoon white pepper, 1 teaspoon dried tarragon
Serve soup up in bowls and garnish with asparagus tips, lemon zest or wedges, and a spoonful of Greek yogurt.
Greek yogurt or creme fraiche for drizzling, Lemon wedges or zest