Place the chicken in a large pot and cover with 10½ cups of water. Bring to a boil, then add the onion, salt, and pepper. Cover and simmer for 1 hour, skimming off any scum that rises, until the chicken is tender and the broth is flavorful. Remove the chicken, let it cool, and shred into pieces. Set aside in a bowl. Strain the stock and return it to the pot.
Heat the oil in a frying pan over medium heat, add the garlic, and cook until lightly browned. Stir in the coriander, then remove from the heat.
Just before you are ready to serve, bring the broth to a boil, add 2 packs of frozen molokhia and reduce to a light simmer for about 10-15 minutes. Remove from heat and leave the pot uncovered until the molokhia has completely thawed. Be careful not to boil or stir, as this can result in separation.
Add the garlic and coriander mix, and stir to combine. If necessary, add some water to achieve the desired consistency and adjust the seasoning to taste.
Serve in bowls with rice or pita bread. The bread can be broken into pieces and then used to scoop the molokhia, or it can be added to the bowl of soup and eaten with a spoon.
