In a medium bowl, combine Greek yogurt, mayonnaise, minced shallot, chopped parsley, chopped cilantro, olive oil, red wine vinegar, minced garlic, and a pinch of kosher salt. Whisk until smooth and creamy.

Mix garlic powder, kosher salt, and black pepper in a small bowl. Pat chicken dry and season with the mixture. Let rest for ten minutes.

Heat avocado oil in a skillet over medium heat. Cook chicken for 4-5 minutes on each side until golden brown and at an internal temperature of 165°F. Rest on a cutting board for five minutes before shredding.

In the same skillet, add diced jalapeño and sliced red onion. Cook for 3-4 minutes until softened.

Shred the chicken with two forks and return to skillet. Fold in chopped cilantro and mix well.

Warm tortillas, layer with shredded romaine lettuce, avocado slices, and chicken mixture. Top with feta cheese and chimichurri sauce. Serve warm.