In a medium bowl, combine Greek yogurt, mayonnaise, chopped shallot, chopped parsley, and chopped cilantro. Drizzle olive oil and red wine vinegar in, then add minced garlic and salt. Whisk until smooth.

In a small bowl, blend garlic powder, salt, and black pepper. Rub this mixture onto the chicken breast and let rest for 10 minutes.

In a skillet over medium heat, add avocado oil. Cook the seasoned chicken for 4-5 minutes on each side until golden-brown and internal temperature reaches 165°F. Let rest for 5 minutes.

In the same skillet, sauté sliced jalapeños and red onion for 3-4 minutes until tender.

Shred the rested chicken and mix with sautéed jalapeños, onions, and chopped cilantro.

Warm tortillas in the microwave. On each, layer romaine lettuce, the chicken mixture, a few slices of avocado, and sprinkle with feta. Drizzle with chimichurri sauce and serve immediately.