Place the meat, garlic, onion, bay leaves, peppercorns, and a teaspoon of salt in a large casserole or pot. Cover generously with water and place over high heat. Once it comes to a simmer, reduce heat to medium low, remove any foam that may have risen to the top, cover, and cook for an hour and a half until the meat is completely tender and falling apart. Turn off heat and set aside.
Once cool enough to handle, remove the meat with a slotted spoon and chop into small pieces. Set aside.
Set a large saute pan over medium-high heat, once hot add a tablespoon of oil. Add the longaniza or chorizo and brown, crumbling into smaller pieces with a couple wooden spoons or spatulas as it cooks, for about 5 minutes until crisp and brown. Add the chopped meat, stir, and cook for a couple minutes until it starts to brown as well. Incorporate the chicharrón, mix it all up and turn off the heat.
Preheat a comal or skillet over medium-low heat. Heat the tortillas for about a minute per side until completely hot with brown specks on both sides. Assemble the tacos, or let people assemble their own, by adding some of the meat mix and topping with chopped onion, cilantro, and salsa callejera.