Toss the chicken breasts and shallots with the olive oil, cumin, paprika and seasoning. Heat a griddle pan on a medium high heat and cook the chicken and shallots until charred and cooked through.
While they are cooking, make the salsa. Add all of the ingredients (reserving some of the chopped echalion to garnish) to a food processor and pulse to a chunky salsa.
To make the guacamole, slice and destone the avocados. Add to a bowl with the rest of the ingredients and roughly mash with a fork.
Warm the tortillas through in a dry frying pan. Thickly slice the chicken.
To assemble the tacos, spread each tortilla with a tablespoon of guacamole. Add a few chicken slices and an echalion half. Top with a generous spoon of the green salsa, and some finely chopped echalion.