In a large skillet, heat the olive oil over medium-low heat and whisk in the flour until smooth and bubbly.
Remove from heat and add the chicken broth and ½ cup of milk, whisking to make sure there are no lumps.
Return to heat and stir in the enchilada sauce. Then whisk in the enchilada sauce. Continue to whisk the mixture as you add the rest of the milk.
In the slow cooker, add beans, tomatoes, frozen corn, onions, and green bell pepper.
Place the chicken on top of this mixture.
Pour the sauce you just made over the chicken.
Cover and cook on low for 6-8 hours or high for 3-4 hours.
Right before serving, take out the chicken and shred it. Then add it back into the pot and mix to combine well.
Top with any optional ingredients: cilantro, sour cream, cheese, avocado.
Store leftovers in an air-tight container for 3 to 4 days or freeze leftovers for up to 3 months.
