Vichyssoise Soup

Ingredients

• 3 tablespoons extra-virgin olive oil, divided
• 4 leeks, well washed and coarsely chopped
• 2 pounds red or white potatoes, peeled and coarsely chopped
• 2 bunches watercress, divided
• 2 1/4 quarts (9 cups) low-sodium chicken or vegetable broth, homemade or store-bought
• 3/4 teaspoon kosher salt
• ground white pepper
• 1 cup half-and-half
• 1 1/2 tablespoons fresh lemon juice, divided
• grated zest of 1 scrubbed lemon
• 2 tablespoons finely snipped fresh chives