Preheat the oven to 350 degrees F.
Roast the peppers by placing them on an open gas flame, turning them frequently withtongs until all sides are charred black, about 7 to 10 minutes. (Alternately, the peppers can be roasted under a broiler, or on top of a gas or charcoal grill.) Place the blackened peppers in a plastic or paper bag, and let rest until cool enough to handle, about 15 minutes. Peel the peppers, split in half lengthwise, and discard the seeds and the stems. Roughly chop and set aside.
Bring a large pot of salted water to a boil. In 3 batches, add the spinach and blanch for 15 seconds. Remove with a slotted spoon and shock in an ice bath. Remove and squeeze out the excess. Chop and set aside.
In a large saucepan, melt 4 tablespoons of the butter over medium-high heat. Add the onions and cook, stirring, until very soft, 3 to 4 minutes. Add the garlic, chili powder, salt, pepper, and cayenne, and cook, stirring, for 45 seconds. Add 1/4 cup of the flour and cook, stirring with a heavy wooden spoon, to make a light roux, 2 minutes. Gradually add the half-and-half, and cook, stirring, until thick, 2 to 3 minutes. Add the spinach and stir to incorporate. Remove from the heat and fold in half of the chopped chiles. Adjust the seasoning, to taste. Fold in the cubed queso fresco and both Pepper Jacks, and set aside.
In a bowl, combine the grated Pepper Jack and cotija. Set aside.
In a skillet, heat 2 tablespoons of oil over medium temperature. One at a time, add the tortillas to the hot oil and cook, turning, until soft and pliable, 15 seconds per side, adding more oil as needed. Remove from the pan and place on a work surface. Place about 1/2 cup of the spinach mixture into the center of each tortilla and roll up into a cylinder. Place, seam side down, in a single layer across the bottom of a 9 by 13-inch casserole dish.
In a saucepan, melt the remaining 4 tablespoons of butter over medium heat. Add the remaining 1/4 cup of flour and cook, stirring constantly with a heavy wooden spoon, to make a light roux. Slowly add the chicken stock and cook, stirring, until thickened, 3 to 4 minutes. Add the cream and cook, stirring, until thick, about 2 minutes. Add the remaining poblano peppers and cook for 1 minute. Pour over the filled enchiladas and bake for 20 minutes. Remove from the oven and cover evenly with the grated cheeses. Return to the oven and bake until the cheeses are melted and bubbly and the enchiladas are completely warmed through, 10 to 15 minutes. Remove from the oven and let sit for 5 minutes before serving.
Serve with Refried Beans and Mexican Rice.
Yield: 6 servings