Another favorite white bean would work well here too. The soaking step speeds up the cooking process, but if you forget, don't fret. As for the vegetables, mince them very very small, and they'll just melt as they cook. Delicious!
1lb. dried great northern beans, soaked overnight if possible and drained
3 carrots, very finely minced
2 stalks celery, very finely minced
1 onion, very finely minced
2-3 cloves garlic, minced
1/2 tsp sage (I buy rubbed sage rather than ground, but ground works)
4c vegetable broth (chicken broth works fine too)
salt and pepper to taste
Drain beans and place beans, carrots, celery, onion, garlic, and sage in the slow cooker. Cover with broth and water. Cover and cook on high for about 8 hours (the beans will be tender after 3-4 hours if you've soaked them beforehand, but the longer it cooks, the creamier the soup gets).
Taste soup and add salt and pepper to taste.
Recipe by one lovely life at http://www.onelovelylife.com/?p=8104