It's really hard to mess up this recipe. The truth is you could just throw all of the ingredients into the pot, place it in the oven, and forget about it. I've even made this with frozen short ribs. But if you have the time, it's worth following a few of these extra steps.
Feel free to use regular balsamic vinegar. But if you want to make a reduction, reduce inexpensive balsamic down until half of it has boiled away.
Season short ribs with salt and pepper. Set aside.
Place large ovenproof pot over high heat. Add bacon fat and vegetable oil. When it's smoking hot, place short ribs in the pan. No need to jiggle or shift the meat around. Just let them do their thing. After 2 minutes, take a peek. When the meat is a gorgeous golden brown, turn to sear on the other side. Remove from pan and set aside.
Turn heat down to medium. Add the onions. Use a wooden spoon and the onions to get all of the meat goodies up off of the bottom of the pot. Once the onions are soft and translucent, turn the heat down to low and add the garlic and anchovies. Stir for a minute. Help the anchovies disintegrate. Pour in the wine. Reduce until it's almost evaporated -- you might need to turn the heat up just a bit.
Add the balsamic and diced tomatoes. Stir. Slide back in the browned short ribs. Bring to a boil, then cover and place in the oven. Check after 1 1/2 hours. The dish is done when the meat is falling off the bones and is easily shredded with two forks. (This takes anywhere from 1 1/2 to 3 hours, depending on the size of your short ribs.)
Cool for a few minutes. Using your hands, slide meat off of the bones. Pick out any large pieces of fat that are unappealing (small ones will melt into the braise). Shred the meat as best you can. Stir. Taste. Add salt if needed. Or a splash of balsamic.
Cover. Place back in the oven until you're ready to eat.
Warm the tortillas. To serve, spoon meat onto the tortillas. Top with crème fraîche and cilantro. Freeze any leftover meat. You will be happy a few weeks down the road.