1. Using kitchen scissors, remove the backbone of the chicken. Turn the chicken over (breast upward) and press down with the heel of your hand to break the breast bone.
2. Put the salt, sugar, bay leaves, garlic and onions in a large glass bowl or nonmetal marinating dish. Add the water and stir until the salt has dissolved. Put the chicken in the brine – if the chicken isn’t completely covered, add more water to the brine. Put in the fridge for 2 hours or overnight.