Prepare the chicken by shredding it into bite-sized pieces. If using raw chicken, boil or grill until fully cooked, then shred.

In a medium bowl, mash the ripe avocado with a fork until smooth. Add Greek yogurt, lime juice, garlic powder, onion powder, salt, and pepper. Mix until well combined.

Take two slices of whole grain bread and spread a generous amount of the chicken and avocado mixture on each slice. Sprinkle 1/4 cup of shredded cheddar cheese on top.

Heat a skillet over medium heat and add olive oil. Place the assembled sandwiches in the skillet and cook for 3-4 minutes on each side until golden brown and cheese is melted.

Remove sandwiches from the skillet, let cool for a minute, cut in half, and garnish with fresh cilantro if desired.