4 serrano chiles
2 garlic cloves
1/2 white onion, coarsely chopped, plus 1 or more thin white onion slices, separated into rings
1 Tbs. canola or safflower oil
1/2 tsp. sea salt, plus more, to taste
1/2 lb. thick tortilla chips
1/4 cup coarsely chopped fresh cilantro
1 cup crema
1/2 cup crumbled queso fresco or mild feta cheese
Put the tomatillos in a small saucepan and add water to barely cover them. Bring to a simmer over medium heat and cook until the tomatillos begin to soften, about 5 minutes. Add the chiles and garlic and continue cooking until the tomatillos are soft, about 5 minutes more. Remove from the heat. Using a slotted spoon, transfer the tomatillos, chiles and garlic to a blender; reserve the cooking liquid. Add the chopped onion and 1/2 cup of the cooking liquid to the blender and process until well blended, leaving some texture. In a large fry pan or cazuela over medium-high heat, warm the oil until it is shimmering but not smoking. Pour in the tomatillo mixture all at once and stir vigorously. Stir in an additional 1/2 cup of the reserved cooking liquid along with the 1/2 tsp. sea salt. Reduce the heat to low and cook, uncovered, until the sauce thickens, about 10 minutes. Add more liquid if necessary. Just before serving, carefully stir the tortilla chips and cilantro into the sauce and continue cooking until softened but not mushy, about 5 minutes. Taste and adjust the seasonings with sea salt. Scoop the mixture into a warmed serving dish or onto warmed individual plates. To garnish, spoon on the crema and scatter the onion rings and cheese on top.