Preheat your oven to 375°F and lightly grease a small baking dish.
Poach or pan-sear the chicken breast until cooked through, then shred it using two forks.
Sauté the diced onion and poblano pepper in a non-stick skillet over medium heat until softened and slightly charred.
In a mixing bowl, combine the shredded chicken, sautéed vegetables, lime juice, sea salt, cumin, and garlic powder.
In a separate small bowl, whisk together the green enchilada sauce and Greek yogurt until a smooth, creamy sauce forms.
Spread two tablespoons of the sauce across the bottom of the baking dish.
Warm the corn tortillas slightly to prevent cracking, then fill each with the chicken mixture and roll them tightly.
Place the tortillas seam-side down in the dish, pour the remaining sauce over the top, and sprinkle with Monterey Jack cheese.
Bake for 15-20 minutes until the sauce is bubbling and the cheese has melted into a golden crust.