2 hours before, prepare the chicken with 1/2 the onions and tomatoes. In a pot over medium heat, melt the margarine and fry the rest of the onions and tomatoes with the garlic. Add the chicken, corn and the green platanos. Cover and cook the meat until the chicken begins to soften (this should take about 45 minutes). after 45 minutes, take out the corn. Add the ripe platanos, yucca, and the potatoes. Salt and pepper to your liking. Cover and continue cooking until potatoes etc are completely cooked. Then put the corn back in. Sprinkle each serving with cilantro and serve hot!