Gently fry the chopped onion and garlic and the finely chopped carrots in a saucepan with a good dash of olive oil for 10 minutes. Add the lentils and vegetable stock. Simmer for a couple of minutes and then blend well to produce a smooth soup. Add salt and pepper to taste.
Make sure there is plenty of liquid, because lentils tend to soak up water and you could end up with a soup that is too thick.
Finish off with a pinch of curry powder and a handful of croutons.