Heat the oven to 180⁰C – Gas 4. Heat the oil in a frying pan and gently cook the onions for a few minutes until soft. Add the pepper, celery and mushrooms and fry for 5 more minutes. Add the grated carrot and fry for 1 more minute.
Remove the pan from the heat, add the remaining ingredients and season with salt and pepper according to your taste. Line a loaf-tin with baking paper and put the mixture in it, pressing it down with a spoon. Bake for 20 minutes until browned on top, and firm. Turn out and serve sliced.