How to Make It
In a small saucepan, cover the tomatillos and chiles with water and cook over low heat until soft. Using a slotted spoon, transfer the tomatillos and chiles to a blender with 1/3 cup of the cooking water and the garlic. Blend until smooth.
In a large skillet, heat 1 tablespoon of oil. Add the tomatillo sauce, season with salt and cook over moderate heat, stirring occasionally, until slightly reduced and flavorful, about 5 minutes. Remove from the heat and keep warm.
In another large skillet, heat 1/4 inch of oil until shimmering. Add half of the tortillas in an even layer and fry over moderately high heat until lightly browned, about 3 minutes. With a slotted spoon, transfer the fried tortillas to paper towels to drain while you fry the rest in the same manner; add a bit more oil to the skillet and lower the heat if necessary.
Drain off all but 1/4 cup of the oil and return all of the tortillas to the skillet. Stir in the onion, cover and cook over low heat, shaking the pan from time to time, until the onion is translucent, about 4 minutes. Add the tomatillo sauce and cook, stirring to blend well, about 3 minutes. Serve at once, topping each portion with the cilantro, cheese and crème fraîche.