In a small bowl, whisk together the Greek yogurt, mayonnaise, minced shallot, parsley, cilantro, olive oil, red wine vinegar, garlic, and kosher salt until smooth. Set aside.

Combine garlic powder, salt, and black pepper in a small bowl and rub this mixture over the chicken breast. Allow to rest for 10 minutes.

Heat avocado oil in a large skillet over medium-high heat. Sear chicken breast for about 4-5 minutes each side until cooked through. Let rest before shredding.

In the same skillet, add water to deglaze and sauté jalapeños and red onion for 3-4 minutes until softened.

Shred chicken and return to skillet with jalapeños and onions. Stir in cilantro and heat for 1-2 minutes.

Warm tortillas, layer with romaine, avocado, and chicken mixture, then drizzle generously with chimichurri sauce and serve immediately.