Cook Cebu lechon by brining the pork belly slab, rolling it in spices and cooking it with a glaze. First, bring 5 cups of water to a boil seasoned with 1 stalk each of lemon grass and scallions, 2 bay leaves, 5 cloves of crushed garlic, 1 tablespoon of ground black peppercorns and 1/2 cup of rock salt. Simmer the brine for 10 minutes before allowing it to cool completely. Pour it over a 5-pound pork belly slab.
After allowing the meat to marinate overnight, rinse it off and pat it dry. Lay the pork belly slab fat side down in a baking dish, and place 1 halved stalk of lemon grass, 1 halved scallion stalk and 2 cloves of crushed garlic in the middle of the pork slab. Roll the pork starting at one side so that the seasonings remain in the middle, and fasten it closed with twine or string.
Whisk together 1 part water and 3 parts evaporated milk, and brush the mixture along the entire outside of the pork roll. Pierce the pork skin with a fork, and place the pork belly on the grated rack of a roasting pan. Cover the meat with foil, and bake it at 375 degrees Fahrenheit for two hours, turning regularly for even cooking. Remove the foil during the last 30 minutes for crispy skin.