This delicious soup freezes well if you want to make a double batch. Children can help you rinse the lentils and prepare the various ingredients.
2 tablespoon olive oil
1 large onion, chopped
1 large leek, chopped
2 medium carrots, chopped
1 red or yellow pepper, de-seeded and chopped
3 garlic cloves, finely chopped
400g can chopped tomatoes
1 bay leaf
1 teaspoon fresh thyme leaves
200g Puy lentils, rinsed
1.5 litres chicken stock
1.5 teaspoons balsamic vinegar
Freshly ground black pepper
Heat the olive oil in a medium heavy-based pan over a medium heat and add the onion, leek, carrots and pepper. Cook, stirring occasionally, until the vegetables begin to soften, about 2 minutes. Add the garlic and cook for 1 minute. Stir in the tomatoes, bay leaf and thyme, cook for a further minute.
Stir in the lentils and season with pepper, cover, reduce the heat to medium-low, and cook until the vegetables have softened, 8 to 10 minutes.
Uncover, increase the heat to high and add the stock or water. Bring to the boil, then cover partially, and reduce the heat to low. Simmer until the lentils are tender but still hold their shape, about 30 to 35 minutes. Discard the bay leaf.
Puree 700ml of the soup in a liquidiser or with a hand blender until smooth, then return to the pan. Stir in the balsamic vinegar and reheat the soup over a medium-low heat until piping hot.
Tip: This soup can be made in advance. After adding the vinegar cool to room temperature and refrigerate for up to 2 days.