Preheat oil to 325 degrees in a large cast iron skillet.
In a separate medium-sized cast iron skillet, pour the 2 tablespoons of olive oil and place the skillet over medium heat. Add the onions and caramelize, about 5 minutes, stirring occasionally. Add the poblano strips and cook for 1 minute. Add the chicken and reduce the heat to low. Cook the chicken over low heat for 4 minutes to reduce the water content. Remove from heat and set aside.
Using a pair of tongs, dip the tortillas in the hot oil for a couple of seconds to soften them. This will make the tortillas flexible enough to roll. Transfer to a bowl.
Working on a clean, flat surface or cutting board, place 3 tortillas overlapping each other. Place about 2 tablespoons of shredded chicken spread out in the center of the tortillas. Tightly roll the tortillas and secure with toothpicks, especially where the tortillas overlap. Place on a sheet pan. Repeat the process with the rest of the tortillas. Working in batches, carefully drop the rolled tacos into the hot oil and fry until crispy, about 3 minutes, turning the flautas once. Transfer them onto a sheet pan lined with paper towels to absorb the excess oil. Repeat the process for the rest of the rolled tacos.
Garnish with shredded lettuce. Accompany with salsa de aguacate and sour cream.
Add the tomatillos, cilantro, onion and serrano peppers into a food processor and pulse four times. Add the avocado, lime juice and salt and pulse four times. Makes 2 cups
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