Chilaquiles With Queso Fresco

1 1/2 pounds tomatillos, husks removed
1 serrano chile (about 1/2 ounce), stem removed
3 small garlic cloves (about 1/4 ounce)
2 large stems fresh epazote (leaves only), available in ethnic markets and well-stocked supermarkets
1/4 cup safflower or other light vegetable oil
10 stale corn tortillas (about 6 inches in diameter), cut in strips or in eighths, or an equivalent number of packaged “restaurant-style” tortilla chips (about 40 chips if they are each 1/4 of a tortilla)
salt to taste
4 tablespoons crema agria, crème fraîche, or sour cream
4 ounces queso fresco (or other salty, crumbly white cheese), shredded or cut in small cubes
1/2 small white onion (about 2 ounces), thinly sliced

Simmer the tomatillos and chile in enough water to cover until tomatillos are soft, 8 to 10 minutes. Put in a blender with garlic and just enough water to make a smooth but still textured purée and blend for a few seconds. Add epazote and blend for a few seconds more. Set aside.

In a medium skillet heat the oil and fry the tortilla pieces in batches until deep golden brown. Drain on paper towels. (If using prepared chips, break them into bite-size pieces, about 2 by 2 inches.) If necessary, add more oil to skillet to make about 1 tablespoon; add tomatillo mixture, and “fry” it for about 10 minutes. It should bubble lightly. Add a little water if the sauce is thick, season with salt, and cook for 5 more minutes.

Briefly stir in tortilla chips, turn heat off, cover skillet, and let sit for 5 minutes to let chips soak up sauce. Top each serving with crema agria, queso fresco, and sliced onions. Note: You may also put a fried egg on top of each portion. Serves 4.