Saute the onions, garlic and carrots in the olive oil for 10 minutes.
Add the lentils, tomato puree, oregano and 500ml of the vegetable stock.
Bring to the boil then reduce to a simmer. Check frequently and add more stock if necessary.
Simmer for 20 minutes or so until the lentils are soft.
Buzz in a food processor or with a stick blender but leave some texture.
To make the drizzle, place the Marmite in a jug then simply add an equal amount of boiling water. Stir well and drizzle on your soup to your heart's content.
Recipe by Veggie Runners at https://www.veggierunners.com/2013/03/07/lentil-soup-with-marmite-drizzle/