How do I use a slow cooker properly?

What slow cookers are genuinely good at, the adjustments recipes need, and the safety points that matter.

Difficulty: beginner
Time: 8 hr
Read: 3 min
Safety: caution

Short answer

Brown meat and soften onions in a pan first — a slow cooker can't brown, and skipping it gives a pale, flat result. Use less liquid than a conventional recipe, since nothing evaporates, and don't lift the lid, which adds substantial time each time.

Slow cookers excel at tough cuts and anything that benefits from long, gentle cooking. What they can't do is brown, reduce or crisp — which is why food cooked entirely in one often tastes flat. Ten minutes in a frying pan first solves most of it.

Safety

Don't put frozen meat in a slow cooker — it spends too long in the temperature range where bacteria multiply before reaching a safe temperature. Red kidney beans must be boiled hard for 10 minutes before slow cooking, as a slow cooker alone doesn't reliably reach a high enough temperature to destroy their natural toxin. Fill it between a third and two-thirds full for safe, even cooking.

What you'll need

Slow cooker
Frying pan for browning
Meat thermometer (optional)

Step by step

Brown meat in a hot frying pan before it goes in.The browning is where a large share of the flavour comes from, and a slow cooker cannot produce it.
Soften onions and other aromatics in the same pan.Deglaze the pan with stock or wine and pour that in too — the browned residue is pure flavour.
Reduce the liquid compared with a conventional recipe — often by a third or more.Almost nothing evaporates in a slow cooker, and ingredients release their own liquid. Too much is the commonest complaint.
Fill the cooker between a third and two-thirds full.Under-filled and it can burn; over-filled and it heats unevenly and can overflow.
Put root vegetables at the bottom, meat on top.The base is the hottest part, and root vegetables take longer than most people expect.
Don't lift the lid.Each peek loses heat and can add 20–30 minutes. There's nothing to see anyway.
Add dairy, fresh herbs and anything delicate in the last 30 minutes.Cream and milk can split over long cooking, and fresh herbs lose everything.
If the sauce is thin at the end, reduce it in a pan or add a cornflour slurry.Or take the lid off for the last half hour on high — though that's slower than a pan.

Tips

Slow cookers suit cheap, tough cuts — shin, shoulder, brisket, thigh. Lean, expensive cuts dry out and are a waste of both money and the method.
Low for 8 hours and high for 4 are broadly equivalent, but low generally gives better texture for tough cuts.
You can prepare everything the night before, refrigerate the pot, and start it in the morning — check your model allows the pot to go in cold.
A slow cooker uses very little electricity compared with running an oven for the same time.

Common mistakes

Not browning first — You lose the Maillard flavour entirely, which is why some slow cooker food tastes flat.
Using a conventional recipe's liquid quantity — Nothing evaporates, so it ends up watery. Reduce by a third or more.
Cooking frozen meat from frozen — It stays too long in the bacterial growth range before reaching a safe temperature.
Lifting the lid to check — Each time costs significant heat and adds substantially to the cooking time.

Questions people ask

Do I have to brown the meat first?

Not for safety, but it makes a large difference to flavour. A slow cooker cannot brown, and browning is where much of a stew's depth comes from.

Why is my slow cooker food watery?

Almost always too much liquid. Conventional recipes assume evaporation, which barely happens in a slow cooker. Reduce the liquid by a third or more.