For me, this is one of those dishes that is the epitome of home cooking: it's not delicate or particularly photogenic, though in person it does look like autumn in a bowl. One would be hard pressed to find this in a restaurant. Warm, it is a complete dinner that comes together in under an hour. It remains completely satisfying cold the next day and therefore great to pack for lunch. I always make an enormous bowl to get several meals out this.
Preheat the oven to 350 degrees and start to heat water for your couscous. Put the chicken breasts on a large sheet pan (yes, this is way too big for them). Season both sides of the chicken breasts with salt, pepper, coriander, and paprika. Rather than give exact amounts here, it is better to go by how it looks: you want the chicken breasts to be nicely coated, but not overwhelmed. Add cayenne if you want some heat. Drizzle some olive oil over each chicken breast and put them in the oven. Roast until the internal temperature reaches 165 degrees, roughly 20-25 minutes, flipping them once.
While the chicken roasts, prepare the vegetables: peel, de-seed, and chop the squash into half-inch cubes; peel the parsnips and cut into inch-long segments; cut any especially wide segments in half the long way. Peel the shallots, and slice each one into three or four rings, depending on their length. Put all of the vegetables in a large bowl, toss with enough olive oil to gently coat them. Season generously with salt and pepper, and add coriander and paprika to taste. Again, if you want some heat, add some cayenne.
Cook the couscous: if using Moroccan, put the couscous in a bowl and add 3/4 cups boiling water; cover and let set for a few minutes, then fluff with a fork. For Israelli couscous, cook as if you were making pasta. After it is done, add a few drops of olive oil to stop it from clumping.
When the chicken is done, take it out of oven, turn up the heat to 400 degrees. Let the chicken rest on a plate and add the vegetables to the tray (don't clean it-- that's good flavor on the tray!), and spread them into a single layer. Roast until tender 25-35 minutes.
While the vegetables roast, make the dressing: add all the ingredients into a small bowl and whisk until everything incorporated. Taste it to make sure it is your liking.
(Alternatively, you can roast the chicken breasts on a small tray and the veggies on a large tray at the same time at 400. The chicken will cook faster so make sure it doesn't dry out).
After the chicken has cooled a little, use two forks and shred the chicken. In a large bowl, mix the chicken and the couscous and toss to combine.
Chop the parsley medium-fine and crumble your cheese of choice. Don't add this to chicken couscous mixture yet.
After the veggies are tender, add them to the chicken and couscous mixture and toss to combine. Let cool briefly (so that the hot ingredients don't completely melt the cheese). Then add the dressing, parsley, cheese and toss again.