You could use roasted poblanos, if you can't get the hatch chiles.
Hatch Green Chile Egg Souffle
12 roasted Hatch green chiles
8 cups Mexican quesadilla cheese (cheddar jack can substitute)
3 cups milk
2 teaspoons black pepper
2 teaspoons salt
5 cloves garlic
3 tablespoons flour
Chili powder and green onions to garnish
Preheat oven to 375. Spray a 9 by 13 pan with non-stick spray. Scrape charred skins from chiles and de-seed. Flatten and make a layer on the bototm of the pan with 6 of the chiles. Spread half of the cheese over, then layer the rest of the chiles, and the remainder of the cheese. In a blender, mix the eggs. milk, salt, pepper, garlic and flour until smooth and foamy. Pour over cheese and chiles. Sprinkle with chili powder, and place in oven. Bake for 415-60 minutes unti puffy and middle is set. Let rest for 10-15 minutes, then garnish with green onions and serve.