In a large dutch oven, heat canola oil over medium high heat and add onion, celery and garlic and heat until fragrant, about 1 to 2 minutes
Add white beans, black beans, corn, green chilis, bell pepper, and chicken broth to the pot and cook for 10 minutes, stirring occasionally
Add sour cream and continue heating for 1 minute
Add corn flour, salt, chili powder, cumin, and lemon juice and continue heating for 15 minutes
Check seasonings, adding more if needed.
Add shredded chicken and continue cooking until chicken is heated, about 2 more minutes
Serve with tortilla strips/chips (optional)
Notes
This soup does not freeze well (if gets very gritty when defrosted); if you'd like to freeze, leave out the corn flour and add it when you rewarm the soup.