Preheat oven to 350 degrees. Lightly spray the squash and chopped onion with the olive oil spray, mix well and place on a baking tray. Roast for about 20 minutes or until the vegetables are starting to brown and cooked through. Remove from the oven and set aside.
Lightly spray the chicken breast with the olive oil spray and season with salt and pepper. Place the chicken on a baking tray and roast in the oven for about 10 minutes or until it is just cooked through, turning once. Remove the chicken from the oven. Allow it to cool, then slice it finely on an angle, crosswise. Place the chicken slices in a bowl, and put in the fridge to cool.
To make the dressing, whisk the olive oil, mustard powder, white vinegar, pomegranate molasses, lemon juice and sugar together in a medium-sized bowl.
To make the salad, put the cooked vegetables and chicken slices in a large bowl with the chickpeas, herbs and black sesame seeds. Mix until all of the ingredients are just lightly coated and serve immediately.