Cut the tips of the green bananas and cut the peel of the bananas lengthwise.
Cook the guineitos: In a large saucepan add 2 liters of water, milk and salt to taste. Heat until boiling. Add the bananas and cook for 20 minutes. Drain, let cool and cut into wheels.
Prepare the marinade. In a medium saucepan add all the ingredients for the marinade sauce and cook over medium heat for 10 to 12 minutes. Until the onions are tender. Let it cool.
In a large glass container, add the sauce and add the rest of the ingredients and season to taste.
NOTE: Leave in the refrigerator until serving time. You can add the juice of a lemon at the end.