To prepare the onions, place the thinly sliced onion in a wide-mouthed, roomy, heat-safe mason jar or other storage container. Place the vinegar, sugar, and salt in a mixing bowl. Bring the water to boil, then add it to the bowl and whisk until the salt and sugar are dissolved. Stir in the mustard seeds, then pour this whole mixture over the onions. Allow the onions to sit for about 15-20 minutes. They'll be ready to use, but you can also cover them tightly and refrigerate them for up to a week. The flavors will get more intense as the onions keep.
To prepare the rice, heat 2 teaspoons of coconut oil in a medium sized pot over medium low heat. Add the mustard seeds. When they’ve just started to pop, add the onion. Cook the onion, stirring frequently, for 5 minutes, or until the onion is soft and clear. Add the rice and cook, stirring constantly, until it smells lightly toasted (about 2 minutes).
Add all remaining ingredients to the pot except for the lime juice. Bring the mixture to a boil. Reduce the heat to low, cover, and simmer for 12 minutes, or until the rice has absorbed all the liquid. Remove the rice from heat and allow it to sit, covered, for 10 minutes. Fluff the rice and remove the bay leaf. Squeeze in the lime juice and green onion, if using. If you'd like to add a little moisture, you can drizzle the rice with an additional teaspoon coconut oil. Taste and adjust salt as needed.
Divide the rice into four bowls. Top each with a quarter of the greens and chickpeas and a little scoop of pickled onions. Drizzle with the onion brine or with your dressing of choice. Serve.