1 Peel the onion and chop finely.
2 Peel the potatoes and carrots and cut into 1.5 cm (approximately 1/2-inch) cubes.
3 In a pot, heat 1 tablespoon oil over medium heat, then cook the onion and curry powder until softened. Add 600 ml (approximately 2 1/2 cups) of water.
4 Add potato and carrot cubes to the pot, season with salt and pepper and cook for 5 minutes. Then add the lentils, cover and cook until vegetables and lentils are tender, about 15 minutes.
5 Meanwhile, cut bread into small cubes. Melt butter and remaining oil in a small pan. Toast bread cubes until golden brown, stirring often.
6 Stir the sour cream into the soup, season with salt and pepper and serve topped with croutons.