Preheat the oven to 400 degrees F. Remove the husks, then rinse the tomatillos until no longer sticky; cut into quarters.
In a large bowl, add the tomatillos, poblano peppers, onion, garlic, chicken, oil, 2 teaspoons salt, and 1/2 teaspoon pepper. Toss to coat and distribute ingredients evenly onto a baking sheet. Roast for 25 to 35 minutes or until a thermometer inserted in the chicken registers 165 degrees F.
Remove from the oven and place the chicken on a cutting board. Transfer the tomatillos, peppers, onion, garlic and any pan juices to the bowl of a food processor. Add the cilantro, lime zest, lime juice, 1/2 teaspoon salt and pulse until the mixture resembles a chunky salsa.
Shred the chicken and place in a large bowl. Add the tomatillo mixture and stir to incorporate; add salt and pepper, to taste.
Meanwhile, wrap the tortillas in foil and place in a warm oven until the tortillas are warm, about 10 minutes. Build the tacos by starting with a warm tortilla and add about 1/2 cup chicken mixture. Top the tacos as desired with baby greens, crumbled queso fresco, chopped tomato, and sliced onions.
Cook's Notes: If you have sensitive skin, consider wearing plastic or latex gloves when seeding and chopping the poblano peppers to protect your hands from the pepper's mild heat.
The key to success for the dish is in the roasting. The entire filling ingredients roast for a short time in the oven before being combined, infusing a smoky roasted flavor into the tomatillos and making dinner prep a breeze on busy weeknights.