Creamy, Roasted Poblano Rajas Recipe
Over a gas flame or charcoal fire (if available), roast chilies directly over high heat, turning frequently. You want the heat intense, so the tough skin of the chilies blisters and blackens before the flesh has softened too much. It shouldn't take much more than 5 minutes to roast a chili on an open flame. (When using only one burner, roast the poblanos in batches.) If only an electric stove is available, heat the broiler, adjust the shelf as high as it will go, lay the chilies on a baking sheet and slide them under the broiler. As they blister and blacken, turn them until all are uniformly charred, about 10 minutes.
Whether the chilies are broiler- or flame-roasted, when they are evenly blackened, collect them in a bowl and cover with a kitchen towel to trap a little steam to loosen the charred skin.
When the chilies have cooled enough to be handleable, rub off their charred skin, remove the seedpods, then rinse the peeled, seeded flesh briefly under cool water. Slice the roasted chilies into 1/4-inch-wide strips.
Heat oil over medium-high heat in a very large (12-inch) skillet. When hot, add onion and cook, stirring regularly, until the onion is richly browned but still a little crunchy, about 7 minutes. Stir in garlic and oregano. After a minute or so, when the garlic is fragrant, stir in the chili strips and crema, crème fraîche or heavy cream. When the cream has thickened enough to coat the chilies nicely, which takes only a couple of minutes over medium-high heat (though they need to be stirred nearly constantly), taste the mixture and season it with salt, usually about 1/2 teaspoon.
From More Mexican Everyday: Simple, Seasonal, Celebratory (W. W. Norton) by Rick Bayless.