Put a generous amount of olive oil in a large soup pot and heat on medium-high heat. When the oil is hot, add the onion, leeks and garlic and sweat until softened. Add the carrots, juniper berries, peppercorns and fresh herbs. Then add the chicken wings, turkey necks and soup bones, and brown lightly, stirring constantly and being careful not to burn the onion, leeks and garlic. Finally, add the chicken and pour enough water to cover all the ingredients. Bring to a rolling boil and reduce the heat to a simmer, cooking for approximately 2-3 hours.
Remove the chicken, chicken wings, turkey neck and soup bones to a bowl. When cool enough to touch, pull the meat from the bones and discard the skin, bones, etc. Put in a container or ziploc bag and put in the refrigerator until ready to use.
Put the soup in the refrigerator overnight. The next day, skim off the fat, if desired, and reheat the soup, add the chicken and turkey meat back to the soup. How much is up to you and bring to a rolling boil to cook the matza balls (see below).