Peel and chop the onion, and peel and very finely chop or grate the garlic. Heat a large pan over a medium heat, and fry the onion in the olive oil for 5 minutes until starting to soften. Add the curry powder and garlic and fry for a couple more minutes.
Meanwhile, peel and chop the butternut squash into 2 cm cubes. Add the squash, lentils and stock to the onion mixture, bring to the boil, and simmer for 20 minutes. Stir occasionally to ensure that the lentils don't stick to the pan. The squash should be tender to the point of a knife.
Blitz the soup with a hand blender until smooth. Or if you prefer, use a food processor to blend your soup until smooth. Serve hot.