Season chicken with salt and pepper (optional). Place chicken in the bottom of crock pot.
Add beans, corn, and green chilis to pot on to of chicken.
Sprinkle onion flakes, cumin, and Ranch dressing mix over beans and corn. Stir to combine if desired.
Add chicken broth to the crock pot. Cover and set for 6 hours on low.
About 30 minutes before serving, slightly warm milk (I will usually put it in the microwave for about a minute just to warm it).
In sauce pan over medium heat, melt butter. When butter is melted, add flour. Stir until combined.
Slowly add milk. Stir constantly until the mixture starts to bubble and thicken.
Add cheese and stir to combine. Remove form heat.
Remove chicken from crock pot. Add cheese mixture and stir to combine. Shred chicken and return to the crock pot. Stir again to combine.
Serve hot.