1. Trim roots and dark green leaves from leeks. Halve leeks lengthwise, then slice crosswise into 1" pieces. Transfer to a large bowl filled with cold water. Using fingers, swish leeks to remove dirt, then place in a colander to drain; set aside.
2. Heat oil in a large pot over medium heat until shimmering. Add garlic and cook, stirring constantly, until fragrant, about 30 seconds. Add leeks, celery, potato, 1/2 cup water, and 1/2 teaspoon salt and increase heat to high. Cook, stirring frequently, until water is mostly evaporated and vegetables begin to soften, about 5 minutes.
3. Add broth and bring to a boil. Reduce heat to medium-low and simmer, stirring occasionally, until potato is tender, 6 to 8 minutes. Add chard and cook, stirring frequently, until leaves are tender, 6 to 8 more minutes; stir in parsley and remove from heat.
4. Working in batches, transfer soup to a blender and puree until smooth, about 1 minute, transferring blended soup to a clean pot as you go. Thin soup with a bit of hot water if desired, then season with salt and pepper to taste.
5. Stir Greek yogurt and remaining 2 tablespoons water together in a small bowl, adding more water as needed until thin enough to drizzle. Divide soup among four bowls, then drizzle with yogurt mixture and sprinkle with dill before serving.
Source: Hannaford fresh Magazine, December 2019