In a small pot combine the stock, balsamic and salt. Bring it to a boil, then stir in the quinoa. Cover the pot and turn the heat to medium low. Let the quinoa cook for 12-14 minutes, until all of the liquid is absorbed and it is tender.
Turn off the heat when the quinoa is cooked and fluff it up with a fork. Stir in the chopped spinach and let it just wilt into the hot quinoa. Scoop it onto a plate with your favorite main course and enjoy!