Pick through lentils and remove any stones or debris. Rinse in a fine-mesh strainer under cold running water until the water runs clear. No soaking needed. Optional: set aside aromatics like halved onion, carrot, celery, garlic, and a bay leaf or woody herbs to add during cooking. Keep extra water or broth nearby to top up the pot if needed.

Add rinsed lentils to a medium pot. Cover with cold water or broth — about 2 to 2½ cups liquid per cup of lentils. Add aromatics now if using. Bring to a boil over medium to medium-high heat, then reduce to medium-low for a gentle, steady simmer. Avoid a rolling boil or lentils will turn mushy. Cover and simmer, stirring occasionally. Start checking for doneness at 15 minutes. Green lentils typically take 15–35 minutes at sea level, up to 45 minutes at high altitude. Skim any foam from the surface. If liquid absorbs before lentils are tender, add a splash of water. Hold off on salt until lentils are nearly done — salting early toughens the skins. Once almost tender, season with salt and pepper and cook a final 5–10 minutes until fully done.

Press a lentil against the roof of your mouth — it should smash easily and feel creamy, not chalky. Taste a few from different parts of the pot; they should be tender but still holding shape. Mushy means overcooked and unrecoverable. Once done, remove from heat immediately. To stop cooking fast, add a splash of cold water or a few ice cubes. Drain excess liquid or leave lentils in a little cooking liquid to keep them moist. Remove any whole aromatics (bay leaves, onion halves, carrot pieces) before serving. Keep the simmer gentle throughout — high heat breaks down the outside before the inside cooks. Refrigerate leftovers in cooking liquid for up to 2 days.