Place the chickens in a Dutch oven over medium heat. Pour a little water into the dish containing the marinade and pour into the stewpot.
Turn the chicken every 2 minutes to allow all sides to color.
Pour in the two glasses of water and leave the chickens on their stomachs (breast side down).
Add the chopped onions to the sauce, along with the giblets, cut into small pieces (about 2 cm).
Cover halfway and cook for 45 minutes to 1 hours depending on the size of the chicken. From time to time, pour a little sauce over the top of the chickens. Add a little water if necessary before the end of cooking.
Check for doneness after 45 minutes. A skewer pricked into the chicken breast should penetrate the flesh easily. You should feel that it's cooked.
Once the chicken is cooked, turn off the heat and leave to cool a little so that you can remove the chickens easily.
Drain chickens well before placing on a platter.
Return the pot to the heat to reduce the sauce. The sauce should become very smooth.