Slow cookers have been around for a long time, and they continue to be popular because they're simple and easy to use, they're made to do one job, and they do it well.
That job, in a single word, is braising.
Braising is a cooking technique that involves the long, slow application of moist heat at a low temperature, which has the marvelous effect of breaking down tough cuts of meat and turning them meltingly tender and succulent, while transforming the juices from that meat into a rich, flavorful sauce.
And while they do the same thing for tough root vegetables and sturdy greens like kale and collards, and they can work all kinds of other wonders involving stews, soups and chili, it's with meats and poultry that slow cookers really shine.
Slow cookers are simple devices, comprising a heavy stoneware crock, along with a tight-fitting lid. The crock fits into a unit that generates low heat from underneath. That heat slowly builds up, and the crock holds it in, while the lid ensures that nearly all the steam is recaptured, producing a gentle, moist cooking environment that is ideal for breaking down tough connective tissues in meat.
Like so many culinary traditions, every generation has to rediscover slow cookers for itself. So if you've never used one, here are the basics.
Choose the Right Meat
Because a slow cooker cooks slowly, the best types of meat to cook in one are tough and fatty cuts that require a lot of cooking time. That means things like beef chuck, short ribs, pork shoulder, and spare ribs, to name just a few. But lean cuts like rump roast or sirloin roast can also go in a slow cooker.
The beauty is that roasts like these are easy to overcook in the oven, but in a slow cooker, overcooking them is almost impossible. And of course, you can cook a whole chicken in a slow cooker as well, and while you won't get crispy skin, the finished bird is succulent and tender.
Brown the Meat Before Cooking
While it's true that slow cookers won't produce a crispy exterior on a chicken or roast, that doesn't mean you shouldn't sear those items before putting them into the crock.
The reason is twofold. One, your meats will look nicer when they come out, and two, searing produces all kinds of fabulous flavors as the high heat interacts with the proteins. So be sure not to skip this step. A cast iron skillet is great for searing. Just get it smoking hot, and give the roast about 3 or 4 minutes on each side. Your chickens in particular will benefit from some browning before slow-cooking, as they can come out looking a bit pale otherwise.
Don't Overcrowd the Crock
Each model will have its own guidelines about how full to fill it, but in general it's best not to fill a slow cooker more than two thirds of the way. Overfilling it will make it harder for the unit to reach its target temperature, which can in turn produce a food safety hazard if the temperature remains too low for too long.
And while it's usually necessary to add some sort of liquid to the crock, you can probably get away with less than you think. The cooking process will draw out the juices in the food and since they don't evaporate, those juices become the braising liquid. But again, follow the manufacturer's instructions with respect to adding liquid.
Defrost Frozen Ingredients Before Cooking
You can certainly get away with adding a handful of frozen peas to a slow cooker at the end of cooking your beef stew, but trying to cook a frozen roast or chicken in a slow cooker is not a good idea. This gets back to the issue discussed above relating to temperature and food safety.
Add Dairy Products Last
Dairy products like milk, cheese and cream are emulsified blends of water, fat and protein (in varying proportions: cheese has less water, for instance, and milk has more). And what happens to that emulsion when it spends several hours in a slow cooker is that it breaks apart. The individual components separate, producing a grainy residue of milk solids and water, along with, in the case of cheese, pools of oil. This is not to say that you can't finish your dish with milk or cream, but do so at the very last minute, right before serving.
Practice Slow Cooker Safety
You can feel confident leaving your slow cooker on during the day while you're away (or overnight). This is one of the few kitchen appliances for which this is true, and indeed it's one of the primary advantages of using it. You load it up in the morning, and when you get home your dinner is ready, and your house smells wonderful.
But with that said, if you should happen to get home and discover that there's been a power outage, you have no choice but to toss it. If a pot of meat has been sitting at room temperature all day, it's not safe to eat. This is not one of those situations where you can employ some sort of trick to salvage the meal. You have to throw it out.