8 ounces Yukon gold potatoes, cut into 1/2-inch pieces
1 garlic clove, finely grated
For serving: chopped cilantro, sliced avocado, chopped scallion, and crumbled cotija
For the salsa: Preheat the oven to 475°F. Toss the tomatillos, poblanos, jalapeños, onion, scallions, garlic, oregano, coriander, and cumin with the oil and 1 teaspoon salt on a rimmed baking sheet. Roast until the vegetables are soft and browned, 20 to 30 minutes. Let cool slightly.
Peel the garlic cloves and discard the husks. Strip the oregano leaves from the stems and discard the stems. Transfer the tomatillo mixture along with any accumulated juices on the baking sheet and the garlic and oregano leaves to a blender and purée until smooth. Season with more salt if necessary. Let sit until ready to assemble the enchiladas.
For the filling: Using 2 tablespoons oil, brush both sides of each tortilla. Heat a large skillet over medium-high heat. Working in batches, cook the tortillas until lightly browned and starting to crisp, about 1 minute per side. Set aside until ready to assemble the enchiladas.
Heat 2 tablespoons of the remaining oil on medium-high heat in a large heavy skillet, preferably cast iron. When it begins to smoke, add the mushrooms and cook, tossing frequently, until browned on all sides, about 4 minutes. Transfer to a medium bowl. Add the remaining 2 tablespoons oil to the hot skillet and cook the onion, potatoes, and garlic with 1 1/2 teaspoons salt, tossing occasionally, until lightly browned, about 5 minutes.
Reduce the heat to medium and add the mushrooms, their accumulated juices, and 1 cup water to the potatoes and onions. Cook, stirring occasionally, until the potatoes are very soft and most of the liquid has evaporated, about 15 minutes.
Pour the tomatillo salsa into the skillet and bring it to a boil. Reduce to a simmer. Using a large spoon or wide spatula, push the potatoes, mushrooms, and onions onto one side of the skillet. Working one at a time and using tongs, dip the tortillas in the hot salsa, turning them to coat and leaving them in the salsa until softened, about 3 seconds per side (they will soften more as they sit). Transfer the tortillas to a baking sheet as you go.
Spoon 2 to 3 tablespoons of the vegetables across the center of each tortilla. Fold the tortillas over like tacos. Divide the enchiladas among plates and spoon the remaining salsa over. Top with cilantro, avocado, scallion, and cotija and serve.
Rick Martínez is an award-winning, bestselling cookbook author and host of cooking and travel shows on YouTube. He is a regular contributor to The New York Times and currently resides in Mazatlán with his dog, Choco, where he cooks, eats, and enjoys the Mexican Pacific coast.