3 poblano peppers
1 large onion, roughly chopped
1 1/2 pounds tomatillos, husks and stems removed
2 serrano peppers, stems removed
3 medium cloves garlic, peeled
2 cups homemade or store-bought, low-sodium chicken stock
1 cup loosely packed picked-fresh cilantro leaves and fine stems, plus chopped cilantro for garnish
Kosher salt and freshly ground black pepper
1 1/2 pounds (about 6, 4-6 ounces each) wild Alaska pollock fillets, patted dry
16 soft corn tortillas
8 ounces shredded pepper-Jack cheese, divided
1 cup Mexican-style crema, divided (see note)
1. Adjust broiler rack to 8 inches below element and preheat broiler to high. Place poblanos, onion, tomatillos, serranos, and garlic on a foil-lined rimmed baking sheet. Place under broiler and broil, turning vegetables occasionally, until tomatillos and serranos are completely softened and lightly charred, about 10 to 12 minutes. Transfer tomatillos and serranos to a bowl. Continue broiling until poblanos are charred on all sides, about 2 minutes longer. Transfer to separate bowl and cover tightly with foil. Continue broiling until onion and garlic are softened and charred, about 5 minutes longer. Transfer to bowl with tomatillos along with any juices and set aside.
2. Adjust oven rack to middle position and set oven to 375°F (200°C). Add chicken stock to bowl with poblanos and peel poblanos while submerged in stock. Transfer flesh to bowl with tomatillos, leaving skin and seeds with the stock. Strain stock through fine-mesh strainer into the bowl with tomatillo-pepper mixture. Discard skins and seeds. Add cilantro to mixture. Set mixture aside.
3. Add tomatillo-pepper mixture to Dutch oven. Using an immersion blender, purée mixture into a chunky sauce. Season to taste with salt and pepper. Bring to simmer over medium-low heat. Lightly pat wild Alaska pollock fillets dry and cut in half if they are too long to fit in the pot. Season both sides with salt and pepper and add into the sauce. Cover with lid slightly ajar and simmer until fish is cooked through, about 10 minutes. Meanwhile, wrap tortillas in aluminum foil and place in oven to warm (no longer than 10 minutes).
4. When the fish is cooked, remove from heat and transfer to large bowl using a slotted spatula. Use two forks to gently shred fish (not too small, we don’t want it turning to mush). Add 1 cup of sauce, half of cheese, and half of Mexican crema to bowl and toss to combine. Season to taste with salt and pepper. Remove tortillas from oven and unwrap. Spread 1/3 of the sauce (about 2/3 cup) in bottom of a 13- by 9-inch casserole dish. Dip each tortilla in the remaining sauce and stack on a cutting board. Working one tortilla at a time, place 2 tablespoons of the wild Alaska pollock filling in a line down the center and roll up tightly. Place in the casserole dish seam side down. Continue until all the tortillas and filling are used (the casserole will be tightly packed).
5. Spread remaining sauce over enchiladas and lay remaining cheese down in a line through the middle of each row of enchiladas. Cover tightly with aluminum foil and bake for 10 minutes. Remove foil and continue baking until cheese is lightly browned and bubbly, about 10 minutes longer.
6. Remove enchiladas from oven, drizzle with remaining crema, sprinkle with chopped cilantro, and serve immediately.
Make-Ahead Directions: You can make this recipe the night before you plan to serve it. Simply follow steps one through five, then wrap and chill. Resume at step six the next day. Reheat/bake the dish at a slightly lower temperature until it reaches an internal temperature of 165°F, then crank up heat to brown the cheese.
Note: Mexican-style crema can be found in most Hispanic grocery stores or in the refrigerated dairy section of many supermarkets. If unavailable, substitute with 3/4 cup sour cream whisked together with 1/4 cup milk and 1/4 teaspoon salt.