Prep. Trim the pork butt and beef chuck of excess fat then cut them into 1 1/2 inch (38 mm) cubes.
Cook. In a 12-quart (11 L), or larger, Dutch oven, combine the pork, beef, vinegar, bouillon, 1 tablespoon of the salt, and the pepper with 2 quarts (1.9L) water and bring to a boil over high heat. Decrease the heat to low, cover, and simmer until the meat is fall-apart tender, 2 1/2 to 3 hours.
Using a small, handheld strainer or ladle, skim the scum from the top of the stew and discard. Using a potato masher, mash the meat until all the meat is shredded into the stew.
Finely chop the onion and mince the garlic. Remove the husks and silks from the corn and discard. Grate the corn on the largest holes of a box grater. You'll end up with about 3 cups (720 ml) corn. Add the corn, onion, garlic and tomatoes to the stew and return to a boil. Simmer, uncovered, for 20 minutes. Remove the pot from the heat and cool to room temperature. Refrigerate, covered, overnight.
Serve. Return the pot to the stove and heat over medium-high heat to a simmer. Stir in the remaining 1/2 tablespoon salt and the pepper vinegar and serve.