Place the squash, sweet potato and carrots in a steamer basket; place in a large saucepan over 1 in. of water. Bring to a boil; cover and steam for 12-16 minutes or until tender. Cool slightly. Transfer to a food processor; add juice concentrate. Cover and process until smooth.
Transfer to a large saucepan; stir in the milk, salt and pepper. Cook and stir over low heat until heated through (do not boil). Top each serving with 1-1/2 teaspoons sour cream, 1 teaspoon chives and 1/2 teaspoon sesame seeds.