Fry the bacon cubes and leek rings in a coated pan, add the carrot and celery cubes, continue to fry while stirring, then deglaze with the vegetable stock. Mix the couscous well with 1 tablespoon of olive oil and add to the pan. Put the lid on the pan, switch off the stove and let it soak for 5 minutes. Season to taste with salt and pepper. Serve hot.