When you're first learning to cook, it makes sense to stick to a handful of easy, versatile, tried-and-true ingredients that are simple to work with. Over time, though, as you gain confidence in the kitchen, you'll find that spreading your wings and trying new or strange ingredients can be really rewarding. Oxtails are a prime example of that principle. They're not much used anymore, but they're a much-loved ingredient in traditional cookery and they're perfectly suited for preparation in a slow cooker.
Oxtails Are Really, Really Tough
There's a rule in meat cookery that says the most-used muscles on an animal are almost always the toughest. The heart is a prime example because it keeps working throughout the animal's life. Oxtails fall right into that category as well because tails stay in near-constant motion and their rope-like muscles have to be able to winch them in every direction.
There's a second rule that's closely related to the first, which is that the toughest muscles also tend to be the tastiest. That's because they're dense and filled with fat and connective tissue, and all three of those things contribute to the tastiness of the finished dish. The only thing you need is patience because these cuts need to cook for a long, long time.
Cooking Oxtails Takes Patience
Because tough cuts like oxtail are so dense, it takes time for cooking to soften the muscle fibers and weaken the bonds that hold them together. High temperatures don't help speed things; in fact, they actually make the meat tougher first because the muscle fibers contract when they're faced with intense heat. Low and slow is the way to go, holding the oxtails at a low simmer so the muscles can gently soften and connective tissues can melt into rich, oozy gelatin.
Slow Cooker Oxtails
That need for long, slow cooking means oxtails in a Crock-Pot is a match made in culinary heaven. You'll need to spend a few minutes getting them ready to go, but then you can just ignore them for hours. Your first step is to brown the pieces of oxtail in a skillet or Dutch oven, then transfer them to the slow cooker. Add onions, carrots and celery to the pan and saute them until they soften a bit, then put those in the slow cooker as well.
Finally, drain off the excess fat and pour in a healthy splash of water, wine, broth or other cooking liquid. Stir this around the pan, scraping it to get up all of the tasty brown stuff that's sticking to the pan. Pour the liquid over your oxtails, clap the lid on the slow cooker, and go do something else for the rest of the day. You're looking at a minimum cooking time of 2 to 3 hours on the high setting, or twice that on low.
Finishing Your Oxtail Recipe
Once the oxtails are fork-tender, lift them out of the slow cooker and set them aside in a covered bowl to keep warm. From here you have lots of options, depending what you plan to make. For oxtail soup, you just need to skim the fat from the broth and then shred the oxtail and add it back in. If you want barley or potatoes in the soup, simmer them in the broth before adding back the meat.
For oxtail stew, follow the same steps, except you'll need to thicken the broth with flour or another starch. You can cook potatoes or other vegetables in the broth first, before thickening, or cook them separately and add them to the finished stew after you've thickened it. In either case, it's handy to make your recipe a day ahead of time and chill the oxtail in its broth overnight. The flavors continue to develop, and it's much easier to remove the excess fat once it's hardened in the cold.
You could also set aside the broth for another use, and treat the shredded oxtail itself as the star ingredient. Depending on the seasoning, it makes a fine filling for tacos, empanadas, ravioli or Asian-style dumplings. You can even keep the tender beef in relatively large pieces and serve it in a salad with ripe tomatoes, red onion and a splash of olive oil and good wine vinegar.