Remove papery skins from tomatillos. Cut tomatillos in half and place upside down on baking sheet. Broil 6” from heat until skins begin to blacken. Place tomatillos in plastic bag, let sit for 15-20 min. Remove skins and core; place in blender with jalapeno, 1 clove garlic, 1 tsp. salt and lime juice. Blend to semi-smooth. Set aside. Heat 2 Tbsp. olive oil in large saucepan. Add chicken (or substitute tofu and prepare same way) and brown on 2 sides but do not cook through. Sprinkle with salt and pepper. Remove chicken and add 1 Tbsp. olive oil to pan. Add onions, garlic, cumin and coriander. Cook a few minutes, stirring occasionally until onions are softened. Add chicken, tomatillo sauce, chicken stock, oregano. Stir to combine. Bring to a boil and reduce to a simmer. Cook partially covered for 20 min. until chicken is cooked through. Add cilantro just before serving. For a thicker stew, mix arrowroot with cold water and stir into stew. Boil gently 1 – 2 min. Serve over rice, with sour cream and avocado slices, if desired.