Place the chicken breasts, salsa verde, and pinto beans in a crockpot and cook on low for 4 hours.
When the chicken is cooked through, shred it using 2 forks to pull it apart.
This step is optional but recommended: Lightly toast 8 corn tortillas in a pan over medium-high heat, or on a medium-heat grill
Add 1-2 tablespoons of the sauce to the bottom of a mini casserole dish.
Layer one tortilla, with about ½ cup of the chicken and pinto bean mixture, and about 2 tablespoons of the shredded cheese.
Repeat the above step with another layer tortilla, chicken and bean mixture, and cheese.
Place each casserole dish in the microwave for one minute to melt the cheese (or under the broiler on high heat for about one minute).
Top with pickled vegetables, avocado slices, sour cream as desired.