Preheat oven to 375 F. Lightly grease the muffin tin. Using kitchen shears, cut circles (about 4 inches) from tortilla and press each circle into the hole of a muffin tin. Repeat with remaining tortillas until you have 12 circles. Bake for 5 minutes, then remove.
Meanwhile, in a large bowl, stir together shredded chicken, mango, corn, chives, and 1/2 cup of grated cheese. In a small bowl, stir together Greek yogurt, garlic, salt and pepper. Stir the sauce into the chicken mixture. Gently fold in avocados.
Divide the chicken mixture evenly between the muffin cups and top each cup with a little grated cheese and a few olive slices. Bake for an additional 10 minutes, or until the cheese is melted and the chicken is heated through. Enjoy!