Mix all the marinade ingredients in a large bowl and add the chicken. Cover and leave in the fridge for 6-8 hours. (I've been in a hurry and only left it for 1 hour, and it was still delicious)
In a large pot, bring 3 cups of water to a boil. Add the quinoa with the salt and "spices for cooking the quinoa" and cook for about 7 minutes, until the quinoa is half way cooked. Strain the water from the quinoa.
Saute the onions in butter until lightly brown.
In a large heavy-bottomed pot, put the chicken with all it's marinade in the bottom. Add half of the quinoa. Sprinkle some chopped coriander/mint leaves and the sautéed onions. Then add the remaining quinoa. Cover the dish tightly and cook for 5 minutes on high heat, then 15 minutes on medium heat. Continue cooking on low heat until chicken is cooked through (about 10 more minutes).