Dissolve the stock cube in 1.5 litres of water and boil.
Peel and thinly slice the onions. In a frying pan, fry the onion with a little olive oil. Lightly season with salt and pepper.
Sprinkle the onions with the flour and mix.
Add the onions to the hot chicken stock, cover and simmer for 30 minutes on a low heat. Serve immediately.