Step 1

Slice leeks in half lengthwise. Rinse thoroughly, then discard the root, rough outer edges, and green leafy top. Chop the white and light green portions and set aside.

Step 2

In a medium or large stockpot, heat the olive oil. Cook leeks and garlic over medium heat, stirring, for 3 to 5 minutes. Add the parsley, salt, coriander, and pepper to the pan, cooking for 1 minute longer.

Step 3

Add lettuce and chicken stock to the pot and bring to a boil. Reduce heat and simmer, partially covered, until the lettuce is tender, 1 to 2 minutes.

Step 4

Transfer the soup in batches to a blender, or use an immersion blender, until all soup is thoroughly pureed and creamy.

Step 5

Pour soup back into the pot and stir in the Greek yogurt. Heat, stirring, over medium heat, 1 to 2 minutes. Serve immediately.