Heat a large skillet over medium high heat and sauté onions in vegetable oil, stirring occasionally, until caramelized and most of liquid has evaporated, about 15 minutes. Add halved garlic cloves and saute for 3 minutes more. Stir in spices and seasoning (paprika, salt, garlic and onion powders, black pepper, cayenne, oregano and thyme) and cook for 2 minutes. Set aside.
In a large bowl, stir together the beef stock, ketchup, chili sauce and brown sugar.
Cook the Brisket
Lightly grease crockpot. Place brisket in a crockpot (I had to cut my brisket cut in half and stack it to get it to fit), spread onion mixture over the top, then pour sauce mixture over the entire dish. Cover with the lid and cook it on LOW for 10 hours. (I did this overnight.) Do your best to lift the lid up as little as possible, though if you have a section of the meat sticking out of the sauce, rotate it under the sauce for at least a few hours of the cooking time.)
Rest the Brisket
When the brisket is cooked but still hot, use a spoon to scrape off any large fat deposits adhered to the top and bottom of the brisket. (This part is easiest to do when hot. The sauce will be de-fatted after it has chilled.)
Transfer the brisket and all of its sauce to a baking dish. Chill entire dish in the fridge for several hours and up to one day; this resting time will significantly enhance the flavor and texture of the meat (don't be tempted to skip this step; just do it!)
An hour before you’re ready to serve it
Preheat your oven to 300°F, and remove the dish from the fridge. Remove all of the fat that has solidified on top with a slotted spoon for a less oily finish.
Carefully remove the meat from its sauce and place on a large cutting board. Cut the brisket into 1/2-inch slices.
(Optional: you could run your sauce through a food processor for a smoother sauce; I didn't.)
Carefully place the sliced meat (moving it in large sections with a spatula helps keep it together) back into the sauce and spoon the sauce over the meat. Replace the lid or cover the dish tightly with foil and reheat in the oven until it is bubbling at the edges — this usually takes up to to 30 minutes.
Make the taco shell: Line a baking sheet with a paper towel. Pour enough oil into a large Dutch oven to reach a depth of 2 inches and heat until a deep-fry thermometer reaches 350˚. Working with 1 tortilla at a time, fry, flipping often until the tortilla is light golden, 45 seconds to 1 minute. Using tongs, push down on the center of the tortilla, so the outer edges flare and puff up. Continue to fry until golden brown and puffy, 1 minute more. Remove from the oil and place upside down over a glass cup set over the prepared baking sheet; season with salt. Repeat with the remaining tortillas.
Make the crema: In a small bowl, combine the sour cream and spices. Stir. Let sit at least 15 mins for flavors to combine.
Make the black beans: In a small saucepan over medium heat, add the olive oil. When the olive oil is hot, add the onions and season lightly with salt. Cook, stirring often, until soft but not brown, 4 to 5 minutes. Add the beans and water, and cook for 8 to 10 minutes. Stir in the oregano and keep warm on low heat.
Make the grilled tomatoes: Prepare a medium-hot fire in a charcoal grill or heat a gas grill to medium-high heat. Alternatively, place a grill pan over medium-high heat. Brush the tomatoes with the oil and grill, flipping occasionally, until the tomatoes have blistered, 2 to 4 minutes. Season with salt, roughly chop and set aside.
Make the skirt steak: In a small bowl, combine the paprika, cumin, salt, onion and garlic powders, and black pepper. Rub the steak with the seasoning.
Grill the steak, flipping once, until it's lightly charred and cooked to preferred doneness, 3 minutes per side for medium rare. Transfer to a cutting board and let rest for 10 minutes before slicing.
Assemble the taco salad: Drain the black beans and place them in a large bowl. Add the cabbage, grilled tomatoes, radishes, cilantro and mint. Add the olive oil, season with salt and toss.
Divide the cabbage mixture among the 4 taco shells. Top each taco shell with the steak, avocado slices, jalapeño or serrano rounds, and Cotija. Garnish each shell with a lime wedge and serve with the crema.
