1. Place the chicken breasts between two sheets of parchment paper.
2. Pound the chicken to an even ½-inch thickness using a meat mallet.
3. In a large bowl, combine the olive oil, ground garlic, cumin, chili powder, and kosher salt. Add the chicken to the bowl and coat thoroughly, massaging the seasoning into the meat.
4. Cover and marinate for at least 30 minutes, or refrigerate overnight for deeper flavor.
5. Preheat your grill to high heat and lightly oil the grates.
6. Grill the marinated chicken for 2–3 minutes per side with the lid closed, or until fully cooked through.
7. Transfer the grilled chicken to a plate and let it rest before slicing into bite-sized pieces.
8. In a large mixing bowl, whisk together the lime juice, avocado oil, ground garlic, cumin, chili powder, kosher salt, and freshly ground black pepper to make the dressing.
9. Add the diced grilled chicken, black beans, corn kernels, red bell pepper, chopped cilantro, jalapeño, and red onion to the bowl with the dressing.
10. Toss until all ingredients are evenly coated.
11. Gently fold in the diced avocado and Cotija cheese, if using.
12. Taste the salad and adjust the seasoning if needed.
13. Garnish with extra cilantro and toasted pepitas, if desired, and serve.