Heat a flat-top griddle to 500 degrees F and preheat oven to 250 degrees F.
Melt 1 tablespoon butter on the griddle. Sprinkle the oxtails with salt and pepper, then sear, about 3 minutes per side.
Meanwhile, rough chop carrots, celery and onion (mirepoix).
Remove oxtails and set aside.
Put mirepoix and garlic on base of a hotel pan or roasting pan and place oxtails directly on top. Cover with root beer and ox stock (ensure meat is covered with liquid) and cover tightly with foil.
Roast until meat is fall-off-the bone-tender, about 10 hours.
Remove oxtails from pan, then let cool in a large bowl. Shred meat off bone, discarding bones and large chunks of fat; set aside bones for stock, if desired.
For the taco assembly: Saute ox meat with the root beer syrup (just enough to hydrate, not enough to reseason meat) in a frying pan. Place on a warmed corn tortilla, top with Pineapple and Roasted Jalapeno Salsa, crumbled chicharrones and a drizzle of Agave Hot Sauce. Finish with cilantro and enjoy your trip to Flavortown.
Pineapple and Roasted Jalapeno Salsa:
Mix together the pineapple, cilantro, jalapeno, onion, garlic, salt, pepper and lime juice in a bowl. Season to taste with salt, pepper or lime.
Agave Hot Sauce:
Mix together the hot sauce and agave in a bowl until incorporated well.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.