Place the chicken in a large pot with the cumin, salt, pepper, and the water. Place the garlic, onions and scallions in a blender with ¼ cup of water and blend. Add this mixture to the pot.
Bring to a boil, reduce heat and simmer for about 30 minutes.
Add half of the cilantro, corn and plantains. Season with salt and pepper and cook for about 30 minutes more or until the plantains are tender.
Remove the chicken from the pot, de-bone it, breaking the meat into bite sized pieces, and return the meat to the soup. Sprinkle with chopped cilantro and serve warm.