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

Season the chicken breasts with garlic powder, salt, and black pepper. Rub seasoning evenly and let rest for 10 minutes.

In a skillet, heat oil over medium heat. Cook the chicken for 4-5 minutes on each side until golden brown and fully cooked. Allow to rest before shredding.

Deglaze the skillet with a splash of water. Add sliced jalapeño and red onion, sautéing for 3-4 minutes until tender.

Shred the chicken using two forks, then combine it with the sautéed vegetables and cilantro in a large bowl.

To assemble, take a flour tortilla, add romaine lettuce, then avocado slices, and the chicken mixture. Top with feta cheese and drizzle with chimichurri sauce. Serve warm.