In a small bowl, mix together the ancho chile powder, ground cumin, 1 teaspoon sea salt and ground coriander. Sprinkle the chicken's both sides with the mixture and set aside.

Using a grill or the grate of your gas stove, place the corn atop the flame to char for 2 to 3 minutes, rotating it every so often so it gets an even char. Remove from the grate and cut off the kernels.

In a small bowl, mix together the charred corn kernels, diced tomatoes, jalapeño, shallot, juice from 1 lemon and a few pinches of salt. In another small bowl, add the diced avocado and juice from 1 lemon. Mash up with a fork, until smooth, and add a few pinches of salt to taste.

In a medium skillet, set over moderately high heat, add a tablespoon of olive oil. When the oil is hot, add the chicken and cook on the first side for 1 to 2 minutes, until browned; flip the chicken and cook on the opposite side for an additional 2 minutes. Turn the heat down to medium low. Remove the chicken and quickly dice (a pair of tongs in one hand and a knife in the other help make this go very quickly!) it up and return it to the pan, adding more oil if needed. Cook for an additional 2 to 3 minutes. Remove

Divide the pieces of lettuce among plates. To assemble, place a few spoonfuls of chicken into each lettuce cup. Top with a tablespoon of the tomato mixture and a dollop of guacamole.