Start with the chicken. Place chicken pieces, 1/2 of the onion cut into slices, 2 cloves of the garlic, the 1 bay leaf, 1 teaspoon black peppercorns and 2 teaspoons of the salt in a large saucepan.

Cook the chicken. Cover with water by 2 inches and place over medium-high heat. Bring to a boil, then reduce the heat to a simmer and cook until chicken is very tender, about 40 minutes.

Shred chicken. Remove chicken from broth (strain and save broth for another use) and let cool. Shred into bite-sized pieces discarding any skin or bone, season with salt, and set aside. You can do this step the day before or use store-bought rotisserie chicken.

Roast poblanos. Place 2 poblano peppers over the open flame of a gas stove set to medium-high heat. Roast, turning frequently, until charred and blackened on all sides. Remove to a heatproof bowl and cover with plastic wrap. Let sit until cool enough to handle.

Peel and chop poblanos. Peel off the blackened skin of the poblanos. Cut off the stem and remove the seeds. Rinse under cold water to get off any remaining bit of skin and seeds. Chop into large pieces, transfer to a bowl and season with salt.

Simmer veggies for the sauce. Combine the pound of tomatillos, remaining onion half, sliced, remaining 2 garlic cloves and, the 3 serrano chiles in a large saucepan. Cover with water by an inch and bring to a boil. Reduce to a simmer and cook until vegetables are soft, about 10-15 minutes.

Blend. Drain and transfer to a blender with the 1/2 cup cilantro, 3 teaspoons salt, and 1 1/2 cups sour cream. Blend on high until smooth. Be careful when blending hot liquid, cover the blender with a thick paper towel instead of the lid to prevent explosions. Pour sauce into a large pie plate or shallow baking dish. Taste and season with more salt if needed.

Get ready to bake. Heat oven to 400°F and grease a 9-inch springform pan.

Fry the tortillas. Heat 3/4 cup of the vegetable oil in a medium frying pan over medium heat. Once shimmering, place 1 tortilla into the oil and fry until golden on both sides, about a minute. Transfer to a baking sheet lined with paper towels, sprinkle with salt, and repeat with remaining tortillas, adding more oil 1/4 cup at a time if needed.

Start layering. Dip a tortilla in the green chile sauce until coated on both sides and place in the bottom of the prepared springform pan. Continue with three more tortillas spreading them out in the bottom of the pan to cover as much surface area as possible.

Stack. Top with half of the chicken, half of the poblano peppers, and a third of each cheese. Repeat with another layer of 4 sauce-coated tortillas, remaining half of the chicken, remaining half of the poblanos, and another third of the cheese. Press down on the pastel to make it all fit in the pan. Coat the remaining tortillas in the sauce and place on top and scrape any remaining sauce over the enchiladas spreading to coat evenly. Sprinkle the remaining cheese on top of the tortillas. Press down again so that nothing is overflowing. It is okay if the tortillas crack and break a little.

Bake. Place the pan on a baking sheet to prevent spills and bake until the cheese is browned and the sauce is bubbling, about 30 minutes. Remove and let sit for 5 minutes before removing the sides of the pan. Sprinkle with crumbled cotija cheese if you'd like.

Serve. Slice into wedges and serve garnished with ripe avocado, shredded lettuce, and more Cotija sprinkled on top. Pastel Azteca can also be cooled, wrapped tightly in plastic wrap and frozen for up to 3 months. Thaw completely, then remove plastic wrap, cover with foil and bake at 400°F until heated through, about 20 minutes.