Lentils are inexpensive, versatile and useful for everything from soup to salads, but different varieties behave quite differently in a saucepan. Red split lentils soften quickly and tend to break down. Many green and brown lentils retain their shape and need longer cooking. If you treat them as interchangeable, you may end up with a watery soup when you wanted a firm salad.
Start by checking the packet. Good Food's guide to lentil varieties says ordinary dried lentils generally don't need soaking and can take around fifteen to forty minutes, depending on the type and the texture you want. The instructions for your particular lentils and recipe should take priority over a single universal timer.
Choose lentils for the dish you are making
Split red lentils are useful when you want the lentils to thicken a soup, dal or sauce. They often cook down into a soft, almost creamy texture.
Green and brown whole lentils generally hold together better, making them useful in warm salads, stews and side dishes. Their cooking time varies with the variety and age of the dried lentils.
Puy-style lentils are prized for a pleasantly firm bite. Use a recipe written for them if you want separate grains in a salad rather than a thickened soup.
Tinned lentils have already been cooked. They usually need rinsing or draining according to the label and can be added towards the end of a recipe, rather than simmered from dry for half an hour.
Do lentils need soaking first?
Most ordinary dry lentils don't require overnight soaking. That's one reason they're convenient compared with some larger dried beans.
Rinse them through a fine sieve under cool running water, and look through the batch for small stones, damaged grains or other debris. Even well-packed pulses deserve a quick check before cooking.
If your packet explicitly recommends soaking, follow it. Some specialised products or recipes may use a soak for a particular result, but don't assume it's mandatory for every lentil.
Soaking is also not a substitute for cooking. If the product is raw and dry, it still needs suitable heat treatment before eating.
The basic saucepan method
Put rinsed lentils into a suitable saucepan with enough fresh water or stock to cover them generously. Exact quantities vary because red lentils intended for soup use a different amount of liquid from green lentils you plan to drain.
Bring the liquid to a boil, then reduce the heat to a gentle simmer. Stir occasionally, particularly if you're cooking split lentils that can settle and stick to the bottom.
Start tasting towards the early part of the cooking window. Some red lentils soften in around fifteen minutes, while whole green and brown lentils commonly take longer.
If the pan starts drying before the lentils are tender, add a little hot water and keep the heat low. Don't let the bottom scorch while you're waiting for the centres to soften.
How to cook red lentils
Use red split lentils when the goal is a thick soup or dal. After rinsing them, simmer in a generous amount of water or stock and stir from time to time.
As they soften, the individual pieces lose their shape and make the liquid cloudy and thick. That is normal, not evidence that the lentils have been overcooked.
A good dal may need additional liquid depending on the other ingredients and how long you cook it. Add water gradually until it reaches the texture you want.
If the lentils are still gritty, they need longer. Cook them until the pieces are thoroughly soft before serving rather than relying on their colour alone.
Cooking green and brown lentils for salads
For a salad, aim for tender lentils that remain distinct when you stir them. Use plenty of simmering water, then drain when they are done.
Start checking with a spoon well before the maximum time on the packet. Taste several grains from different parts of the pan to make sure they are evenly cooked.
Once drained, a little olive oil, lemon juice and chopped herbs can make a pleasant warm side dish. If the lentils are going into a cold salad, cool them promptly and refrigerate them appropriately.
Don't continue boiling them simply because a recipe lists a longer time. Lentils that have already reached the desired texture may begin breaking apart if they remain on the hob.
Why some lentils stay hard
Old dried lentils or those stored in poor conditions may take longer to soften. A pan that is barely warm may also fail to simmer them properly.
Check that the water is gently bubbling and the lentils remain submerged. Add small amounts of hot water when necessary.
Some recipes add acidic ingredients such as tomatoes or lemon juice during cooking. Depending on the legume and recipe, acids can affect softening. If the lentils repeatedly stay firm, try cooking them mostly in plain water before adding acidic ingredients.
A few hard grains mixed among tender ones may indicate uneven heat, inadequate stirring or a product with mixed sizes. Don't serve crunchy undercooked lentils and expect them to soften on the plate.
Cooling and storing cooked lentils
Like other cooked foods, lentils should be cooled promptly and placed in the fridge rather than left in a warm saucepan overnight. The Food Standards Agency recommends a fridge temperature of 5°C or below.
Use clean shallow containers and refrigerate portions soon after cooking. If you combine lentils with meat, dairy or other perishable ingredients, follow the most restrictive applicable storage guidance.
Label any portions you freeze and keep them in suitable sealed containers. Cooked red lentil soup freezes differently from a green-lentil salad: the soup usually tolerates a softer thawed texture.
Reheat a chilled portion until it is thoroughly hot, stirring to eliminate cold spots. Don't repeatedly reheat an entire batch when you only need one serving.
What if your lentils turn to mush?
First check which kind you bought. Split red lentils are supposed to soften and disintegrate in many recipes, so a creamy texture isn't a failure in a soup.
Whole green or brown lentils can turn mushy if cooked too long or stirred aggressively after they become tender. Drain them as soon as they reach the texture the recipe requires.
If a salad batch has gone too soft, it may still be useful in a blended soup or as the base for savoury patties, provided it has been handled and stored safely.
Next time, choose the right variety, taste during cooking and remove the pan from heat before the lentils lose their shape.
The easiest way to get consistent results
Keep a note of the variety you liked and the cooking time that worked on your hob. A split red-lentil soup and a firm green-lentil salad call for different methods, even though both begin with dried pulses.
Buy sensible quantities, store dried lentils in a cool dry place and check the packet for cooking directions. Rinse, simmer and taste: that is enough for most everyday lentil dishes.
Sources reviewed
Good Food: types of lentils and how to cook them and Food Standards Agency: safe storage temperatures.