Make the chicken: Place chicken in a slow cooker, pour chicken broth over chicken. Cover with lid and cook on low 5 hours (or until chicken is cooked through). Shred and set aside.
Make the enchilada sauce: Combine all enchilada sauce ingredients in a blender and blend for a minute or two until everything is very well blended. Pour sauce into a medium non-reactive saucepan and bring just to a boil over medium high heat. Reduce heat and simmer 20 minutes, until sauce thickens.
Warm the tortillas: Preheat a non-stick griddle over medium heat. Cook corn tortillas on preheat griddle about 20 seconds per side or until pliable. Immediately stack tortillas on a plate after being warmed and cover with a pan lid (this seals in the moisture and helps them become flexible without cracking).
Preheat oven to 350 degrees F.
Assemble and bake the enchiladas: To prepare enchiladas, place about 1/4 cup shredded chicken in the center of tortilla, cover with 1 tablespoon enchilada sauce followed by 2 tablespoons shredded Monterrey Jack cheese. Roll tortilla and place seam-side down in a 13" x 9" baking dish.
Repeat this step with remaining tortillas, arranging enchiladas side by side in dish. Cover top of each rolled enchilada with 2 tablespoons enchilada sauce. Cover enchiladas with remaining cheese.
Bake in preheated oven for 14 -16 minutes until cheese is bubbling and enchiladas are heated through. Serve with sour cream.
Notes
You can make the green enchilada sauce in advance and freeze it for later use.