Heat 1 Tbsp. olive oil in skillet over medium heat. Add onions and poblano pepper. Cook 5 minutes, or until soft and translucent. Add chile powder and oregano, cook 1 minute. Add salsa and enchilada sauce, stir well. Add chicken, covering with sauce, and simmer 20 minutes, or until chicken is cooked through, flipping chicken once during cooking process.
Meanwhile, heat 1 tsp. vegetable oil in skillet over medium heat. One at a time, lightly fry tortillas on each side. Cool on a paper towel or wire rack. (This helps prevent the tortillas from getting too soggy during cooking).
Place jalapeños on a baking sheet and toss with 1 Tbsp. olive oil. Broil 6-8 minutes, turning once, until lightly charred and soft. Remove jalapeños and set oven to 350°F.
Remove chicken from sauce and shred. Add 2 cups sauce and 1/2 cup shredded cheese to chicken and gently mix. Divide chicken among tortillas, rolling each one tightly and place in a greased 13x9-inch baking dish. Pour remaining sauce over tortillas, taking care to spread to outer edges. Top with remaining cheese.
Bake 20-30 minutes, or until hot and bubbling and cheese is melted and lightly browned. Remove from oven and let cool 5-10 minutes. Top with avocado, cilantro, sour cream and roasted jalapeños.