Step 1

Put the curry powder into a large saucepan, then toast over a medium heat for 2 mins. Add the olive oil, stirring as the spice sizzles in the pan. Tip in the onions, apple, garlic, coriander stalks and ginger, season, then gently cook for 5 mins, stirring every so often.

Step 2

Meanwhile, peel, then grate the sweet potatoes. Tip into the pan with the stock, lentils, milk and seasoning, then simmer, covered, for 20 mins. Blend until smooth using a stick blender. Stir in the lime juice, check the seasoning and serve, topped with roughly-chopped coriander leaves.