First you’ll need to roast the chiles in order to peel the tough skin. Place the chiles under the broiler until blackened, about 5 minutes per side. Place the chiles in a paper sack or plastic food-storage bag, close it tight and let the chiles steam for 20 minutes. Take the chiles out of the bag and gently rub off the skin. Remove the stem and seeds and dice the chiles.
Meanwhile, in a large, deep skillet, melt the butter on medium-low heat. Add the onion and cook until translucent, about 5 minutes. Add the garlic and cook for 30 more seconds. Add the squash, and then while occasionally stirring, cook until the squash is softened, about 5-7 minutes. Stir in the cilantro, salt, black pepper, and cumin. Turn off the heat. Taste and adjust seasonings.
Preheat the oven to 350°F and grease a 3-quart baking dish. (If your skillet is oven proof and holds this amount, you can just use that instead.)
For easier mixing, transfer the squash to a large mixing bowl. Add the diced chiles, flour, and baking powder. Stir until well distributed. Add the cheese and again, stir until well combined. Whisk together the eggs with then milk and then pour over the squash and stir until well combined.
Lightly sprinkle half the crushed saltines along the bottom of the baking dish. Pour in the squash mixture into the dish and then sprinkle the rest of the saltines on top. Bake uncovered for 30-35 minutes or until the casserole is set and the top is lightly browned in places.
Serve warm. If you want to take it to a gathering, it can easily be reheated.
Squash and green chile casserole | www.homesicktexan.com