Cook base veggies until soft. Add stock and simmer until potatoes are fork-tender.
Puree in a blender and pass through a chinois.
Meanwhile, take remaining onion, carrots, and celery stalks and brunoise (that means fine dice, champ).
Cut cabbage into 1" x ½" pieces. Put all veggies into soup and cool. Add salt and soy.
Garnish with julies (scallions), diced red peppers, and something purple like beets or red cabbage.