2 tablespoons butter
3 small leeks, sliced
1 clove garlic, chopped
1 quart chicken stock
2 medium Yukon Gold or russet potatoes, peeled and chopped
1 teaspoon salt
1 bunch asparagus, roughly chopped and woody ends discarded
1 cup milk
Juice of half a lemon
Freshly ground pepper to taste
Heat the butter in a large pot over medium heat. Add the leeks and sauté until soft, but not browned, about 10 minutes. Add the garlic and cook for another minute.
Add the chicken stock, potatoes, and salt to the pot and bring to a boil. Reduce heat to a simmer, cover and cook for 15 minutes.
Add the asparagus and simmer for 10 minutes.
Remove the soup from the heat and let it cool for about 15 minutes. Add the milk, lemon juice, and pepper.
Transfer the soup to the blender and blend until smooth. Depending on the size of your blender, you may need to blend in batches.
Taste for seasoning, stirring in more salt, pepper, or lemon juice if necessary.
Chill for at least six hours (and preferably overnight) before serving. If the soup seems too thick before serving, add more milk or chicken stock.