Carrot and lentil soup

It feels like the middle of autumn at the moment, so I made soup for lunch from some chicken stock that was lurking at the back of the freezer.

Makes enough for three or four:

one onion
a couple of sticks of celery
some chicken stock (or failing that, a stock cube/vegetable bouillon powder)
a couple of handfuls of lentils (red are good for this, as they go nice and sludgy)
four or five carrots

Chop up the onion and celery and fry together in a little olive oil until they are softened. Add the carrots (chopped), the lentils, and the chicken stock. Depending on how concentrated your stock is, you may need to add some more water - you want about a litre of liquid.

Season with salt and black pepper. You could add some cumin to this, but I've never really found it enhances it much.