How to convert any recipe into a slow cooker recipe
Whether you call it a slow cooker, a Crock-Pot or God's gift to the strapped-for-time cook who likes from-scratch meals, it's one of the handiest pieces of equipment in your kitchen. If you have existing family favorites that weren't written for the slow cooker, that doesn't mean you need to have time to stand over the stove to eat them. You just need a little slow cooker-conversion know-how.
Pay attention to your protein
The slow cooker's strength is how tender and juicy it can make inexpensive, tougher cuts of meat, but you truly can cook anything you want. Many people advise against using things like boneless, skinless chicken breasts (meats that traditionally turn out tender and juicy without a lot of work), but I give you permission to ignore them. I've done it many times myself, and it turns out just as tender and juicy as a brisket. Just keep an eye on it to prevent overcooking, but there's a lot more margin for error with those than some would have you believe.
Generally, it's best to sear the outside of your meat before you put it in the slow cooker, unless you're looking for a shredded texture. Not only does it give it that brown color and caramelized flavor you would expect from the non-slow cooker version, but it lets you get rid of some of the excess fat.
Hamburger and crumbled sausage should be fully cooked, browned and drained prior to putting it in the slow cooker, or it will get mushy and probably be a rather unappealing color. Meats that come fully cooked, like some sausages, should be sliced (if they're supposed to be) and browned first as well. The same applies to vegan proteins like tofu.
Seafood should also be seared first (very quickly so as not to overcook it) and added in the last half-hour of cooking.
The vegetable variable
One of the most important things you should consider when converting a recipe for use in the slow cooker is the vegetables. How hardy are they? Are they supposed to be browned or softened in the recipe? What size are they as compared to the meat? Compared to each other?
Rule numero uno with veggies in a slow cooker is that all the veggies that go in together (at the same time) should be cut to approximately the same size, regardless of what the recipe says. That way they'll cook evenly.
Things that should be browned or softened, like onions and garlic, shouldn't usually be put in raw, or they'll be too strong in the finished dish. I recommend charring them first, though browning them first is also fine. Just cut them into pieces approximately the same size as the other veggies you'll be putting in, and char the outside on a griddle or cast-iron skillet. Onions should be quartered or eighthed (depending on the size of the onion and the other veggies that will go in with it). Garlic should be kept whole in the skin. You can peel and chop it after it cools. If you decide to brown them, be mindful that onions tend to disintegrate on long cooks, especially on high heat, so consider adding it about halfway through cooking.
Rule numero dos is timing. Hearty vegetables, especially root vegetables like carrots, onions, potatoes and turnips, can go in at the beginning of the cooking process. They should be layered on the bottom of the meat to ensure more even cooking.
Vegetables that are less hardy but not specifically quick-cooking, like broccoli and cauliflower, should go in about halfway through. Quicker-cooking veggies like peas, corn and spinach should go in about half an hour before the end of cooking.
Never use frozen vegetables in a slow cooker. They'll bring down the temperature of the cooking liquid and not only add cook time but may also put your food in the danger zone for bacteria. It's OK on the stovetop or in the oven when you can control the temperature by increasing it, but you can't do so in the slow cooker. And if you defrost them, they'll be soggy going in.
Get your grain in
Pastas and rice should be added in the last half hour of cooking. Watching America's Test Kitchen one day, I saw they recommend using parboiled (precooked) rice in the slow cooker, so I tried it, and it worked beautifully. (As an added bonus, it turns out I prefer parboiled rice in a lot of ways… it has a slightly buttery flavor that adds a lot to many dishes.)
Be deliberate with dairy
Dairy won't do well in the slow cooker for long periods. Liquid dairy or creamy solids (like sour cream) will curdle, and aged cheeses will get oily. If you're making something like a cream soup, use vegetable or chicken stock instead of milk during the actual cooking process, and add enough heavy cream in the last half-hour to get that creamy consistency. If your dish uses a splash of dairy or melted cheeses, do the same.
Let's talk liquid
A slow cooker recipe requires liquid to act as a conductor of the slow cooker's heat (thereby cooking the food). So if your recipe doesn't have any liquid added, you should add about 1-1/2 to 2 cups to get the process started. You can always add more boiling water later if need be. If there's too much water when it's done, just take the lid off, and let it keep cooking until the liquid steams off.
That said, if the recipe does have liquid and it's intended to be a long-cook recipe where the liquid would cook off (like a stew), you'll want to reduce the amount of liquid by about half, leaving enough to cover the food in the slow cooker. Since the lid stays on the slow-cooker, the liquid won't reduce much. Just remember, if you decrease it too much and decide you need more, you need to add boiling water to avoid lowering the cooking temperature.
If your recipe relies on a roux to thicken it, you can't start with that, or you'll end up with cement, but all is not lost. Cook it as usual but without the roux. About half an hour before the end, ladle about 2 cups of the hot liquid out of the slow cooker, replace the lid, and turn the heat to high if it isn't already there. Make your roux on the stovetop, being careful to reduce the roux by half if you reduced your cooking liquid by half. When your roux is ready, slowly ladle in the liquid you pulled out, whisking constantly to avoid lumps, until it's all combined. Then pour the thickened liquid back into the slow cooker, stir to combine, and cook for an additional half-hour.
Liquid seasonings (like liquid smoke or Worcestershire sauce), dry herbs or hearty fresh herbs (like rosemary) and seasonings that aren't too strong (like sweet paprika) can usually be added at the beginning, though you should usually reduce the amount you use (you can always add more). Delicate fresh herbs (like cilantro or parsley) and strong spices (like cumin or chipotle) should be added toward the end in the last half-hour and can be added in their full amounts (along with the rest of any spices you added earlier you feel you need more).
If your recipe calls for wine, I recommend reducing it on the stovetop first. In most recipes the wine is cooked in an open pot or pan, so much of the alcohol cooks off and mellows, while the other flavors intensify and get sweet. That won't happen in a slow cooker because the lid is on. If you want to add it without pre-reducing it, do so toward the end, and cook it with the lid off.
A special note about salt: Be careful salting early on, especially if you're using salty liquids like store-bought stocks. The salt can intensify in some dishes as it cooks, and in slow cookers, you can't taste after you add raw meat. Remember that you can always salt toward the end after the meat is cooked. Halve the salt up front, and add more in the last half-hour of cooking if necessary.
Converting cooking times
Obviously your slow cooker takes longer to cook dishes (it's literally in the name). It will always vary by dish, but in general, you can use a formula to get a starting point. Then the first time you make it, just start checking it at the beginning of the lower time. Don't be afraid to turn from high down to low part of the way through cooking if you need a little more time. It's best to keep the lid on as much as possible during cooking, but it's OK to check it every so often after the four-hour mark on low or the hour-and-a-half mark on high (before that, it's unlikely to be done, because it takes a long time to come up to temperature). The chart below will give you a starting point.
- Oven/stovetop: 15 – 30 minutes = Low: 4 – 6 hours = High: 1-1/2 – 2-1/2 hours
- Oven/stovetop: 31 – 40 minutes = Low: 6 – 8 hours = High: 3 – 4 hours
- Oven/stovetop: 41 minutes – 3 hours (or more) = Low: 8 – 10 hours (or more) = High: 4 – 6 hours (or more)