Given the task definition and input, reply with output. In this task, you will be presented with the directions of a recipe separated by "," and have to fill in the "___" which is a step that is missing from the recipe.

Bring the potatoes, broth or water, and salt to a boil in a soup pot; turn down and simmer slowly for about 20 minutes.,Add the leeks, garlic and spinach during the last 5 minutes.,Use a food processor or hand blender to puree the soup and all the veggies until smooth. You will probably have to do this in batches in the processor.,Transfer the soup to a container, cover tightly and chill for about 4-5 hours or overnight.,Stir in the buttermilk just before serving and add white pepper to taste.,______
Sprinkle on the fresh dill for garnish.