1.Place barley in large saucepan. Cover with water; bring to a boil. Reduce heat to low; cook uncovered for 30 minutes or until tender. Drain; reserve. (Can be made 1 day ahead to this stage and refrigerated, covered).
2.Heat oil in large saucepan; cook onion, carrot, celery and garlic over medium heat, stirring occasionally, about 10 minutes or until vegetables are almost tender.
3.Remove corn kernels from cobs. Add corn kernels, parsnip, stock and the water to pan; cook, uncovered, over medium heat for 15 minutes or until almost tender. Add pumpkin; cook further 5 minutes or until all vegetables are tender.
4.Stir in barley and parsley; cook until heated through. (Can be made 1 day ahead to this stage and refrigerated, covered).
5.Stir 1 teaspoon of miso into each cup of heated hotpot.