Place the quinoa in a pan with the stock cube and water. Cook as per pack instructions (usually this is 600ml of water for 200g quinoa, then boil and simmer for 20 mins). Place the baby spinach in the pan on top of the quinoa and place a lid on for the last minute to wilt the spinach. Remove the lid and leave to cool.
Make the vinaigrette by whisking all of the vinaigrette ingredients together.
Place the chopped avocado in a bowl with the lemon juice, garlic salt and pepper. Mash together roughly with a fork (I like to leave a mine quite lumpy and rustic looking).
Place the cooked quinoa in a large serving bowl. Top with the salad leaves, sliced chicken, wilted spinach, mashed avocado, red onion slices, cherry tomatoes and crumbled feta. Sprinkle with parsley before serving with the vinaigrette.