Method:
Heat 1/2 cup broth in a large pot over medium-high heat. Reduce heat to medium, add leek and cook, stirring often, until tender, about 6 minutes. Add remaining broth and potatoes and bring to a boil. Stir in asparagus and broccoli and return to a boil. Reduce heat to medium-low and simmer gently until vegetables are tender, 15 to 20 minutes. Remove pot from heat and set aside to let cool slightly.
Carefully transfer soup to a blender and purée in batches until smooth. Ladle soup into bowls, garnish with chives and serve.