Pour the beef stock into the cooking pot. Bring to a boil.
Add garlic and onions until texture turns soft.
Mix whole peppercorn, dried bay leaves, and soy sauce.
Add the leftover lechon. Let it simmer for 30 to 35 minutes.
Pour vinegar and bring to a boil. Let it simmer for 10 minutes.
Mix the sugar and lechon sauce. Simmer for another 5 minutes.
Sprinkle salt to taste and stir.