Place pistachios in a food processor or blender and pulse until finely diced. Sprinkle half of the pistachios onto a large plate.
Warm oil in a frypan over medium-high heat. Press chicken breast halves into the pistachio pieces adding more crushed nuts to the plate as needed. Sprinkle chicken breasts with garlic powder and black pepper.
Place chicken in the frypan and cook until golden brown. Reduce heat to medium low and cook for about 3 to 5 minutes on each side until the chicken is no longer pink inside. Remove chicken to a cutting board and slice into thin slices.
To serve; place equal amounts of spinach leaves, tomatoes, avocado, capsicum and spring onions into four bowls. Place chicken slices on top. Sprinkle with Parmesan then pour on Balsamic vinegar. Season with black pepper.