Heat cast iron skillet over medium-high heat, and add olive oil.
Add the onion and saute 3-4 minutes. Add garlic, poblano, bell pepper, chili powder, salt and pepper. Saute until the vegetables begin to soften, about 3 minutes more.
Add the tomatillos saute about 1 minute.
In a medium bowl, whisk together the eggs, 1/4 teaspoon salt, and a few grinds of pepper.
Add the eggs to the skillet. With a spatula, gently fold them into the sauce. Continue to fold the eggs into the sauce, allowing the uncooked eggs to flow to the bottom of the pan. Add the tortilla chips. Cook until the eggs set folding this chips in as the eggs cook. Stir in the brisket, salsa, and cilantro.
Transfer the migas to heated plates. Optionally, sprinkle with cheese and avocado. Serve with black beans.