Acorn Squash and Granny Smith Apple Soup

Place squash cut side down on rack set over gently simmering water in saucepan. Cover and steam until tender, about 10 minutes. Cool squash slightly. Scoop the pulp from the shells. Combine 1/4 cup chicken stock, apples and onion in heavy medium saucepan. Cover and cook over low heat 10 minutes. Add squash pulp, remaining chicken stock, apple juice, ginger and salt. Cover and simmer until ingredients are very tender, about 20 minutes. Pure soup in batches in processor or blender. Strain through sieve into clean saucepan, pressing pure with back of spoon. Reheat soup gently. Add lemon juice. Season with a generous amount of pepper and adjust salt to taste. Ladle into bowls. Garnish with yogurt and chives