Warm 1 tablespoon olive oil in a large skillet over medium heat. Season both sides of chicken with Cajun seasoning, and place in hot oil. Stir in crushed garlic. Cook chicken 5 minutes on each side, or until juices run clear. Remove chicken from skillet,
drain on paper towels, cool slightly, and dice; discard oil and garlic.
In a small bowl, mix remaining olive oil, balsamic vinegar, mustard, salt, and pepper.
In a large bowl, gently toss the dressing with the mixed salad greens, arugula, avocado, sun-dried tomatoes, and olives. Top with diced chicken to serve.