4 serrano chile peppers, top cut off to expose interior and to remove stems
3 cloves garlic
1 cup white or yellow onion, chopped
1/4 of a whole white or yellow onion
1 bunch cilantro, rinsed and chopped, stems included
High smoke point cooking oil such as canola oil, peanut oil or grapeseed oil
12 corn tortillas
3 Tbsp sour cream
1/2 cup crumbled Mexican Cotija or Queso Fresco cheese
1 Put chicken thighs in a medium sized saucepan and just cover with water. Add one clove of garlic that has been cut in half, 1/4 of an onion, and 1 teaspoon of salt to the water. Bring to a boil, reduce to a low simmer, and cook, covered, for 20 minutes, until the chicken is just cooked through. Remove chicken thighs to a separate bowl and let cool enough to touch.
2 While the chicken is cooking, put the tomatillos and 3 serrano chile peppers in a separate sauce pan and cover them with water. Bring to a boil, reduce to a simmer. Simmer until the tomatillos are cooked, and have changed color, but are not mushy, about 5 minutes. Remove from heat. Use a slotted spoon to transfer tomatillos and serranos to a blender. Add 1/2 cup of the tomatillo cooking liquid to the blender, as well as 2 cloves of garlic, a third a cup of your chopped onion, and about 1/4 cup of chopped cilantro (packed). (Remaining chopped onion and cilantro will be used for garnish.) Add one teaspoon of salt. Purée until completely blended, 15 to 30 seconds. Taste for heat. If not spicy enough add another chile pepper (doesn't have to be cooked). Note that sour cream will eventually be added to the sauce which will cool down a lot of the spiciness. Add more salt to taste if necessary. Pour sauce into a skillet, bring to a simmer and let simmer for 5 minutes. Then remove from heat.
3 Remove the cooked chicken meat from the bones. Shred the meat with a fork or knife. Put the chicken in a bowl and add 1/3 to a 1/2 cup of the tomatillo sauce to the chicken. Taste the chicken; if it needs salt, add a little.
4 Heat a tablespoon of oil in a frying pan on medium high heat. Add a tortilla to the pan and use a metal spatula to flip it to the other side. Place another tortilla on top of this one (to soak up the excess oil) and flip again. When the tortillas are heated through, remove them to a plate lined with paper towel. Add a little more oil to the pan, and add another couple tortillas. Continue to heat through and soften all of the tortillas. Note that if you are using just made homemade tortillas you can skip this step because the tortillas are already hot, softened, and ready to eat.
4 Warm the oven to 200°F. Dip a tortilla in the salsa verde tomatillo sauce and place it on an oven-proof serving dish. Scoop a spoonful of chicken into the center of the tortilla and roll up the tortilla. Place on the serving dish and repeat with all of the tortillas. Put into the warm oven to keep the enchiladas warm while you finish the sauce.
5 Heat the salsa verde sauce again until simmering, then remove from heat. Stir in the sour cream until well blended. Remove the warming enchiladas from the oven and pour salsa verde sauce over all of them. Top with chopped onion, cheese, and cilantro.
Serve immediately. Serve with extra garnishes of onion, cheese, and cilantro on the side.