Summer Squash Potato Soup

1.Cut the squash into 2-inch pieces, leaving the skin on. Place in a large soup pot. Peel the potatoes if you like, cut them into 1-inch pieces, and add them to the squash. Cover the vegetables with the stock, and bring to a boil. Reduce the heat, cover, and simmer until the squash and potatoes are tender, about 20 minutes. Then add the butter, 1 tablespoon of dill, and a good pinch of salt and pepper. Remove from heat. Puree the soup in a blender, food processor, or food mill, or with an immersion blender, until smooth. Return it to the soup pot and heat through, stirring in the remaining 2 tablespoons of dill. Serve hot, sprinkling with scallions or chives.